diff --git a/.dev-lib b/.dev-lib
index 25f81df2221..663a5ce0043 100644
--- a/.dev-lib
+++ b/.dev-lib
@@ -1,6 +1,8 @@
 PATH_EXCLUDES_PATTERN=includes/lib/
 DEFAULT_BASE_BRANCH=develop
 ASSETS_DIR=wp-assets
+PROJECT_SLUG=amp
+SKIP_ECHO_PATHS_SCOPE=1
 
 function after_wp_install {
     echo "Installing REST API..."
diff --git a/.travis.yml b/.travis.yml
index 66fc489ed79..c7e4d9968e7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,31 +4,10 @@ language: php
 # Opt to use Travis container-based environment.
 sudo: false
 
-# PHP version used in first build configuration.
-php:
-    - "7.1"
-
-# WordPress version used in first build configuration.
-env:
-    - WP_VERSION=latest
-
 # Newer versions like trusty don't have PHP 5.2 or 5.3
 # https://blog.travis-ci.com/2017-07-11-trusty-as-default-linux-is-coming
 dist: precise
 
-# Next we define our matrix of additional build configurations to test against.
-# The versions listed above will automatically create our first configuration,
-# so it doesn't need to be re-defined below.
-
-# WP_VERSION specifies the tag to use. The way these tests are configured to run
-# requires at least WordPress 3.8. Specify "latest" to test against SVN trunk.
-
-# Note that Travis CI supports listing these above to automatically build a
-# matrix of configurations, but we're being nice here by manually building a
-# total of four configurations even though we're testing 4 versions of PHP
-# along with 2 versions of WordPress (which would build 8 configs otherwise).
-# This takes half as long to run while still providing adequate coverage.
-
 notifications:
   email:
     on_success: never
@@ -39,24 +18,7 @@ cache:
     - node_modules
     - vendor
     - $HOME/phpunit-bin
-
-matrix:
-  include:
-   - php: "5.3"
-     env: WP_VERSION=latest DEV_LIB_SKIP=phpcs
-   - php: "5.3"
-     env: WP_VERSION=4.7 DEV_LIB_SKIP=phpcs
-   - php: "5.4"
-     env: WP_VERSION=latest
-   - php: "5.4"
-     env: WP_VERSION=4.7
-   - php: "7.0"
-     env: WP_VERSION=latest
-   - php: "7.0"
-     env: WP_VERSION=4.7
-     # 7.1 / latest already included above as first build.
-   - php: "7.1"
-     env: WP_VERSION=4.7
+    - $HOME/deployment-targets
 
 install:
   - nvm install 6 && nvm use 6
@@ -68,3 +30,40 @@ script:
 
 after_script:
   - source $DEV_LIB_PATH/travis.after_script.sh
+
+jobs:
+  include:
+    - stage: test
+      php: "7.2"
+      env: WP_VERSION=trunk
+    - php: "5.3"
+      env: WP_VERSION=latest DEV_LIB_SKIP=composer,phpcs
+    - php: "5.4"
+      env: WP_VERSION=4.7    DEV_LIB_SKIP=composer,phpcs
+    - php: "5.5"
+      env: WP_VERSION=latest DEV_LIB_SKIP=phpcs
+    - php: "5.6"
+      env: WP_VERSION=4.8    DEV_LIB_SKIP=phpcs
+    - php: "5.6"
+      env: WP_VERSION=latest DEV_LIB_SKIP=phpcs
+    - php: "7.0"
+      env: WP_VERSION=latest DEV_LIB_SKIP=phpcs
+    - php: "7.1"
+      env: WP_VERSION=latest DEV_LIB_SKIP=phpcs
+    - stage: deploy
+      if: type = push AND fork = false AND ( branch =~ ^[a-z][a-z0-9-]{0,10}$ OR branch =~ ^[0-9]+\.[0-9]+$ ) AND NOT branch IN ( live, test, dev, settings, team, support, debug, multidev, files, tags, billing )
+      php: "7.1"
+      env: WP_VERSION=latest DEV_LIB_ONLY=composer,grunt
+      script:
+        - |
+          eval "$(ssh-agent -s)"
+          pantheon_branch=$( echo $TRAVIS_BRANCH | sed 's/^\([0-9]\)/v\1/' | sed 's/[^a-z0-9-]/-/' )
+          echo "Initializing deployment to Pantheon branch: $pantheon_branch"
+          openssl aes-256-cbc -K $encrypted_7eb11f40d4e9_key -iv $encrypted_7eb11f40d4e9_iv -in bin/keys/id_rsa_ampconfdemo.enc -out bin/keys/id_rsa_ampconfdemo -d
+          chmod 600 bin/keys/id_rsa_ampconfdemo
+          ./bin/deploy-travis-pantheon.sh \
+            ampconfdemo \
+            db7f3307-9808-4753-aaa4-acb387c94472 \
+            $(pwd)/bin/keys/id_rsa_ampconfdemo \
+            $pantheon_branch
+      after_script: skip
diff --git a/Gruntfile.js b/Gruntfile.js
index c0baa9fd8b3..fc2bd647957 100644
--- a/Gruntfile.js
+++ b/Gruntfile.js
@@ -1,5 +1,6 @@
 /* eslint-env node */
 /* jshint node:true */
+/* eslint-disable no-param-reassign */
 
 module.exports = function( grunt ) {
 	'use strict';
@@ -76,33 +77,81 @@ module.exports = function( grunt ) {
 	] );
 
 	grunt.registerTask( 'build', function() {
-		var done = this.async();
+		var done = this.async(), spawnQueue = [], stdout = [];
 
-		grunt.util.spawn(
+		spawnQueue.push(
 			{
 				cmd: 'git',
-				args: [ 'ls-files' ]
+				args: [ '--no-pager', 'log', '-1', '--format=%h', '--date=short' ]
 			},
-			function( err, res ) {
-				if ( err ) {
-					throw new Error( err.message );
+			{
+				cmd: 'git',
+				args: [ 'ls-files' ]
+			}
+		);
+
+		function finalize() {
+			var commitHash, lsOutput, versionAppend;
+			commitHash = stdout.shift();
+			lsOutput = stdout.shift();
+			versionAppend = commitHash + '-' + new Date().toISOString().replace( /\.\d+/, '' ).replace( /-|:/g, '' );
+
+			grunt.task.run( 'clean' );
+			grunt.config.set( 'copy', {
+				build: {
+					src: lsOutput.trim().split( /\n/ ).filter( function( file ) {
+						return ! /^(\.|bin|([^/]+)+\.(md|json|xml)|Gruntfile\.js|tests|wp-assets|dev-lib|readme\.md|composer\..*)/.test( file );
+					} ),
+					dest: 'build',
+					expand: true,
+					options: {
+						noProcess: [ '*/**', 'LICENSE', 'jetpack-helper.php', 'wpcom-helper.php' ], // That is, only process amp.php and readme.txt.
+						process: function( content, srcpath ) {
+							var matches, version, versionRegex;
+							if ( /amp\.php$/.test( srcpath ) ) {
+								versionRegex = /(\*\s+Version:\s+)(\d+(\.\d+)+-\w+)/;
+
+								// If not a stable build (e.g. 0.7.0-beta), amend the version with the git commit and current timestamp.
+								matches = content.match( versionRegex );
+								if ( matches ) {
+									version = matches[2] + '-' + versionAppend;
+									console.log( 'Updating version in amp.php to ' + version );
+									content = content.replace( versionRegex, '$1' + version );
+									content = content.replace( /(define\(\s*'AMP__VERSION',\s*')(.+?)(?=')/, '$1' + version );
+								}
+							}
+							return content;
+						}
+					}
 				}
+			} );
+			grunt.task.run( 'readme' );
+			grunt.task.run( 'copy' );
+
+			grunt.task.run( 'shell:create_release_zip' );
+
+			done();
+		}
 
-				grunt.config.set( 'copy', {
-					build: {
-						src: res.stdout.trim().split( /\n/ ).filter( function( file ) {
-							return ! /^(\.|bin|([^/]+)+\.(md|json|xml)|Gruntfile\.js|tests|wp-assets|dev-lib|readme\.md)/.test( file );
-						} ),
-						dest: 'build',
-						expand: true
+		function doNext() {
+			var nextSpawnArgs = spawnQueue.shift();
+			if ( ! nextSpawnArgs ) {
+				finalize();
+			} else {
+				grunt.util.spawn(
+					nextSpawnArgs,
+					function( err, res ) {
+						if ( err ) {
+							throw new Error( err.message );
+						}
+						stdout.push( res.stdout );
+						doNext();
 					}
-				} );
-				grunt.task.run( 'readme' );
-				grunt.task.run( 'copy' );
-				grunt.task.run( 'shell:create_release_zip' );
-				done();
+				);
 			}
-		);
+		}
+
+		doNext();
 	} );
 
 	grunt.registerTask( 'create-release-zip', [
@@ -115,7 +164,6 @@ module.exports = function( grunt ) {
 		'jshint',
 		'shell:phpunit',
 		'shell:verify_matching_versions',
-		'wp_deploy',
-		'clean'
+		'wp_deploy'
 	] );
 };
diff --git a/amp.php b/amp.php
index 66b44f38762..5aa304c5939 100644
--- a/amp.php
+++ b/amp.php
@@ -5,7 +5,7 @@
  * Plugin URI: https://github.com/automattic/amp-wp
  * Author: Automattic
  * Author URI: https://automattic.com
- * Version: 0.7-beta1
+ * Version: 0.7-RC1
  * Text Domain: amp
  * Domain Path: /languages/
  * License: GPLv2 or later
@@ -32,7 +32,7 @@ function _amp_print_php_version_admin_notice() {
 
 define( 'AMP__FILE__', __FILE__ );
 define( 'AMP__DIR__', dirname( __FILE__ ) );
-define( 'AMP__VERSION', '0.7-beta1' );
+define( 'AMP__VERSION', '0.7-RC1' );
 
 require_once AMP__DIR__ . '/includes/class-amp-autoloader.php';
 AMP_Autoloader::register();
@@ -55,7 +55,7 @@ function amp_deactivate() {
 	// We need to manually remove the amp endpoint
 	global $wp_rewrite;
 	foreach ( $wp_rewrite->endpoints as $index => $endpoint ) {
-		if ( AMP_QUERY_VAR === $endpoint[1] ) {
+		if ( amp_get_slug() === $endpoint[1] ) {
 			unset( $wp_rewrite->endpoints[ $index ] );
 			break;
 		}
@@ -64,6 +64,15 @@ function amp_deactivate() {
 	flush_rewrite_rules();
 }
 
+/*
+ * Register AMP scripts regardless of whether AMP is enabled or it is the AMP endpoint
+ * for the sake of being able to use AMP components on non-AMP documents ("dirty AMP").
+ */
+add_action( 'wp_default_scripts', 'amp_register_default_scripts' );
+
+// Ensure async and custom-element/custom-template attributes are present on script tags.
+add_filter( 'script_loader_tag', 'amp_filter_script_loader_tag', PHP_INT_MAX, 2 );
+
 /**
  * Set up AMP.
  *
@@ -73,29 +82,13 @@ function amp_deactivate() {
  * @since 0.6
  */
 function amp_after_setup_theme() {
+	amp_get_slug(); // Ensure AMP_QUERY_VAR is set.
+
 	if ( false === apply_filters( 'amp_is_enabled', true ) ) {
 		return;
 	}
 
-	if ( ! defined( 'AMP_QUERY_VAR' ) ) {
-		/**
-		 * Filter the AMP query variable.
-		 *
-		 * @since 0.3.2
-		 * @param string $query_var The AMP query variable.
-		 */
-		define( 'AMP_QUERY_VAR', apply_filters( 'amp_query_var', 'amp' ) );
-	}
-
-	add_action( 'init', 'amp_init' );
-	add_action( 'widgets_init', 'AMP_Theme_Support::register_widgets' ); // @todo Let this be called by AMP_Theme_Support::init().
-	add_action( 'init', 'AMP_Theme_Support::setup_commenting' ); // @todo Let this be called by AMP_Theme_Support::init().
-	add_action( 'admin_init', 'AMP_Options_Manager::register_settings' );
-	add_action( 'wp_loaded', 'amp_post_meta_box' );
-	add_action( 'wp_loaded', 'amp_add_options_menu' );
-	add_action( 'parse_query', 'amp_correct_query_when_is_front_page' );
-	AMP_Post_Type_Support::add_post_type_support();
-	AMP_Validation_Utils::init();
+	add_action( 'init', 'amp_init', 0 ); // Must be 0 because widgets_init happens at init priority 1.
 }
 add_action( 'after_setup_theme', 'amp_after_setup_theme', 5 );
 
@@ -103,7 +96,6 @@ function amp_after_setup_theme() {
  * Init AMP.
  *
  * @since 0.1
- * @global string $pagenow
  */
 function amp_init() {
 
@@ -116,10 +108,16 @@ function amp_init() {
 
 	load_plugin_textdomain( 'amp', false, plugin_basename( AMP__DIR__ ) . '/languages' );
 
-	add_rewrite_endpoint( AMP_QUERY_VAR, EP_PERMALINK );
+	add_rewrite_endpoint( amp_get_slug(), EP_PERMALINK );
 
+	AMP_Validation_Utils::init();
+	AMP_Theme_Support::init();
+	AMP_Post_Type_Support::add_post_type_support();
 	add_filter( 'request', 'amp_force_query_var_value' );
-	add_action( 'wp', 'amp_maybe_add_actions' );
+	add_action( 'admin_init', 'AMP_Options_Manager::register_settings' );
+	add_action( 'wp_loaded', 'amp_post_meta_box' );
+	add_action( 'wp_loaded', 'amp_add_options_menu' );
+	add_action( 'parse_query', 'amp_correct_query_when_is_front_page' );
 
 	// Redirect the old url of amp page to the updated url.
 	add_filter( 'old_slug_redirect_url', 'amp_redirect_old_slug_to_new_url' );
@@ -127,14 +125,16 @@ function amp_init() {
 	if ( class_exists( 'Jetpack' ) && ! ( defined( 'IS_WPCOM' ) && IS_WPCOM ) ) {
 		require_once AMP__DIR__ . '/jetpack-helper.php';
 	}
-	amp_handle_xhr_request();
+
+	// Add actions for legacy post templates.
+	add_action( 'wp', 'amp_maybe_add_actions' );
 }
 
 // Make sure the `amp` query var has an explicit value.
 // Avoids issues when filtering the deprecated `query_string` hook.
 function amp_force_query_var_value( $query_vars ) {
-	if ( isset( $query_vars[ AMP_QUERY_VAR ] ) && '' === $query_vars[ AMP_QUERY_VAR ] ) {
-		$query_vars[ AMP_QUERY_VAR ] = 1;
+	if ( isset( $query_vars[ amp_get_slug() ] ) && '' === $query_vars[ amp_get_slug() ] ) {
+		$query_vars[ amp_get_slug() ] = 1;
 	}
 	return $query_vars;
 }
@@ -150,15 +150,9 @@ function amp_force_query_var_value( $query_vars ) {
  * @return void
  */
 function amp_maybe_add_actions() {
-	$is_amp_endpoint = is_amp_endpoint();
 
-	// Add hooks for when a themes that support AMP.
+	// Short-circuit when theme supports AMP, as everything is handled by AMP_Theme_Support.
 	if ( current_theme_supports( 'amp' ) ) {
-		if ( $is_amp_endpoint ) {
-			AMP_Theme_Support::init();
-		} else {
-			amp_add_frontend_actions();
-		}
 		return;
 	}
 
@@ -168,6 +162,8 @@ function amp_maybe_add_actions() {
 		return;
 	}
 
+	$is_amp_endpoint = is_amp_endpoint();
+
 	/**
 	 * Queried post object.
 	 *
@@ -207,7 +203,7 @@ function amp_correct_query_when_is_front_page( WP_Query $query ) {
 		$query->is_home()
 		&&
 		// Is AMP endpoint.
-		false !== $query->get( AMP_QUERY_VAR, false )
+		false !== $query->get( amp_get_slug(), false )
 		&&
 		// Is query not yet fixed uo up to be front page.
 		! $query->is_front_page()
@@ -219,7 +215,7 @@ function amp_correct_query_when_is_front_page( WP_Query $query ) {
 		get_option( 'page_on_front' )
 		&&
 		// See line in WP_Query::parse_query() at <https://github.com/WordPress/wordpress-develop/blob/0baa8ae/src/wp-includes/class-wp-query.php#L961>.
-		0 === count( array_diff( array_keys( wp_parse_args( $query->query ) ), array( AMP_QUERY_VAR, 'preview', 'page', 'paged', 'cpage' ) ) )
+		0 === count( array_diff( array_keys( wp_parse_args( $query->query ) ), array( amp_get_slug(), 'preview', 'page', 'paged', 'cpage' ) ) )
 	);
 	if ( $is_front_page_query ) {
 		$query->is_home     = false;
@@ -309,9 +305,9 @@ function amp_render_post( $post ) {
 	 * which is not ideal for any code that expects to run in an AMP context.
 	 * Let's force the value to be true while we render AMP.
 	 */
-	$was_set = isset( $wp_query->query_vars[ AMP_QUERY_VAR ] );
+	$was_set = isset( $wp_query->query_vars[ amp_get_slug() ] );
 	if ( ! $was_set ) {
-		$wp_query->query_vars[ AMP_QUERY_VAR ] = true;
+		$wp_query->query_vars[ amp_get_slug() ] = true;
 	}
 
 	// Prevent New Relic from causing invalid AMP responses due the NREUM script it injects after the meta charset.
@@ -333,7 +329,7 @@ function amp_render_post( $post ) {
 	$template->load();
 
 	if ( ! $was_set ) {
-		unset( $wp_query->query_vars[ AMP_QUERY_VAR ] );
+		unset( $wp_query->query_vars[ amp_get_slug() ] );
 	}
 }
 
@@ -364,7 +360,7 @@ function _amp_bootstrap_customizer() {
 function amp_redirect_old_slug_to_new_url( $link ) {
 
 	if ( is_amp_endpoint() ) {
-		$link = trailingslashit( trailingslashit( $link ) . AMP_QUERY_VAR );
+		$link = trailingslashit( trailingslashit( $link ) . amp_get_slug() );
 	}
 
 	return $link;
diff --git a/assets/css/amp-default.css b/assets/css/amp-default.css
new file mode 100644
index 00000000000..d745dd9b186
--- /dev/null
+++ b/assets/css/amp-default.css
@@ -0,0 +1,11 @@
+.amp-wp-enforced-sizes {
+	/** Our sizes fallback is 100vw, and we have a padding on the container; the max-width here prevents the element from overflowing. **/
+	max-width: 100%;
+	margin: 0 auto;
+}
+
+.amp-wp-unknown-size img {
+	/** Worst case scenario when we can't figure out dimensions for an image. **/
+	/** Force the image into a box of fixed dimensions and use object-fit to scale. **/
+	object-fit: contain;
+}
diff --git a/assets/css/amp-playlist-shortcode.css b/assets/css/amp-playlist-shortcode.css
new file mode 100644
index 00000000000..3d8de1c254d
--- /dev/null
+++ b/assets/css/amp-playlist-shortcode.css
@@ -0,0 +1,19 @@
+/**
+* For the custom AMP implementation of the 'playlist' shortcode.
+*/
+.wp-playlist .wp-playlist-current-item img {
+	margin-right: 0;
+}
+
+.wp-playlist .wp-playlist-current-item amp-img {
+	float: left;
+	margin-right: 10px;
+}
+
+.wp-playlist audio {
+	display: block;
+}
+
+.wp-playlist .amp-carousel-button {
+	visibility: hidden;
+}
diff --git a/assets/js/amp-post-meta-box.js b/assets/js/amp-post-meta-box.js
index ecbea808b81..efeadeb7485 100644
--- a/assets/js/amp-post-meta-box.js
+++ b/assets/js/amp-post-meta-box.js
@@ -161,6 +161,8 @@ var ampPostMetaBox = ( function( $ ) {
 		editAmpStatus.fadeToggle( component.toggleSpeed, function() {
 			if ( editAmpStatus.is( ':visible' ) ) {
 				editAmpStatus.focus();
+			} else {
+				$container.find( 'input[type="radio"]' ).first().focus();
 			}
 		} );
 		$container.slideToggle( component.toggleSpeed );
diff --git a/bin/create-gutenberg-test-post.php b/bin/create-gutenberg-test-post.php
new file mode 100644
index 00000000000..75211d31c69
--- /dev/null
+++ b/bin/create-gutenberg-test-post.php
@@ -0,0 +1,175 @@
+<?php
+/**
+ * Creates a post to test all Gutenberg blocks.
+ *
+ * @codeCoverageIgnore
+ * @package AMP
+ */
+
+namespace AMP;
+
+/**
+ * Gets many of the Gutenberg fixture blocks in blocks/tests/fixtures/.
+ *
+ * @throws \Exception If this is script is not run inside the plugin directory, or if it doesn't have .html fixtures.
+ * @return string $content Post content with all Gutenberg blocks.
+ */
+function get_test_block_fixtures() {
+	$gutenberg_dir = dirname( dirname( __DIR__ ) ) . '/gutenberg';
+	$content       = get_test_block_permutations();
+	if ( ! is_dir( $gutenberg_dir ) ) {
+		$gutenberg_dir = dirname( $gutenberg_dir );
+		if ( ! is_dir( $gutenberg_dir ) ) {
+			throw new \Exception( 'Please run this script from the AMP plugin root.' );
+		}
+	}
+
+	$fixtures_dir = $gutenberg_dir . '/blocks/test/fixtures';
+	if ( ! is_dir( $fixtures_dir ) ) {
+		throw new \Exception( "Test files not found in the Gutenberg plugin. You may need to clone the plugin repo: \nhttps://github.com/WordPress/gutenberg.git" );
+	}
+
+	foreach ( glob( $fixtures_dir . '/*.html' ) as $file ) {
+		if ( ! preg_match( '/(serialized|embed|shortcode|custom-text-teaser|core__block)/', $file ) ) {
+			// Add the block's title.
+			preg_match( ':core__(?P<block>.+)\.html:s', basename( $file ), $matches );
+			if ( isset( $matches['block'] ) ) {
+				$content .= sprintf( '<h1>%s</h1>', $matches['block'] );
+			}
+			$content .= file_get_contents( $file ); // @codingStandardsIgnoreLine: file_get_contents_file_get_contents, file_system_read_file_get_contents.
+		}
+	}
+
+	// Replace broken URLs in fixture files.
+	$content = str_replace( 'http://google.com/hi.png', 'https://cldup.com/-3VMmmrPm9.jpg', $content );
+	$content = str_replace( 'https://awesome-fake.video/file.mp4', 'https://videos.files.wordpress.com/DK5mLrbr/video-ca6dc0ab4a_hd.mp4', $content );
+	return $content;
+}
+
+/**
+ * Gets the Gutenberg block permutations.
+ *
+ * These are mostly copied from gutenberg/blocks/test/fixtures/, and slightly modified.
+ * Embeds and shortcodes are tested in a separate script, so this does not have have many.
+ *
+ * @return string $content The blocks as HTML.
+ */
+function get_test_block_permutations() {
+	$blocks = array(
+		array(
+			'title'   => '(Reusable) Block With Video',
+			'content' => sprintf( '<!-- wp:block {"ref":%d} /-->', create_test_reusable_block() ),
+		),
+		array(
+			'title'   => 'Categories With Dropdown',
+			'content' => '<!-- wp:core/categories {"showPostCounts":false,"displayAsDropdown":true,"showHierarchy":false} /-->',
+		),
+		array(
+			'title'   => 'Columns, With 2 Columns',
+			'content' => '<!-- wp:core/columns {"columns":2} --><div class="wp-block-columns has-2-columns"><!-- wp:core/paragraph {"layout":"column-1"} --><p class="layout-column-1">Column One, Paragraph One</p><!-- /wp:core/paragraph --><!-- wp:core/paragraph {"layout":"column-1"} --><p class="layout-column-1">Column One, Paragraph Two</p><!-- /wp:core/paragraph --><!-- wp:core/paragraph {"layout":"column-2"} --><p class="layout-column-2">Column Two, Paragraph One</p><!-- /wp:core/paragraph --></div><!-- /wp:core/columns -->',
+		),
+		array(
+			'title'   => 'Cover Image With Fixed Background',
+			'content' => '<!-- wp:core/cover-image {"url":"https://cldup.com/uuUqE_dXzy.jpg","dimRatio":40} --><section class="wp-block-cover-image has-background-dim-40 has-background-dim has-parallax" style="background-image:url(https://cldup.com/uuUqE_dXzy.jpg)"><h2>Guten Berg!</h2></section><!-- /wp:core/cover-image -->',
+		),
+		array(
+			'title'   => 'WordPress Embed',
+			'content' => '<!-- wp:core-embed/wordpress {"url":"https://make.wordpress.org/core/2017/12/11/whats-new-in-gutenberg-11th-december/"} --><figure class="wp-block-embed-wordpress wp-block-embed">https://make.wordpress.org/core/2017/12/11/whats-new-in-gutenberg-11th-december/<figcaption>Embedded content from WordPress</figcaption></figure><!-- /wp:core-embed/wordpress -->',
+		),
+		array(
+			'title'   => 'YouTube Embed',
+			'content' => '<!-- wp:core-embed/youtube {"url":"https://www.youtube.com/watch?v=GGS-tKTXw4Y"} --><figure class="wp-block-embed-youtube wp-block-embed">https://www.youtube.com/watch?v=GGS-tKTXw4Y<figcaption>Embedded content from youtube</figcaption></figure><!-- /wp:core-embed/youtube -->',
+		),
+		array(
+			'title'   => 'Twitter Embed',
+			'content' => '<!-- wp:core-embed/twitter {"url":"https://twitter.com/AMPhtml/status/963443140005957632"} --><figure class="wp-block-embed-twitter wp-block-embed">https://twitter.com/AMPhtml/status/963443140005957632<figcaption>We are Automattic</figcaption></figure><!-- /wp:core-embed/twitter -->',
+		),
+		array(
+			'title'   => 'Gallery With 3 Columns',
+			'content' => '<!-- wp:core/gallery --><ul class="wp-block-gallery alignnone columns-3 is-cropped"><li class="blocks-gallery-item"><figure><img src="https://cldup.com/uuUqE_dXzy.jpg" alt="title" /></figure></li><li class="blocks-gallery-item"><figure><img src="https://cldup.com/-3VMmmrPm9.jpg" alt="title" /></figure></li><li class="blocks-gallery-item"><figure><img src="https://cldup.com/aMbxBM0zAi.jpg" alt="title" /></figure></li></ul><!-- /wp:core/gallery -->',
+		),
+		array(
+			'title'   => 'Audio Shortcode',
+			'content' => '<!-- wp:core/shortcode -->[audio src=https://wptavern.com/wp-content/uploads/2017/11/EPISODE-296-Gutenberg-Telemetry-Calypso-and-More-With-Matt-Mullenweg.mp3]<!-- /wp:core/shortcode -->',
+		),
+		array(
+			'title'   => 'Caption Shortcode',
+			'content' => '<!-- wp:core/shortcode -->[caption width=150]This is a caption[/caption]<!-- /wp:core/shortcode -->',
+		),
+	);
+
+	$content = '';
+	foreach ( $blocks as $block ) {
+		$content .= sprintf( '<h2>%s</h2>', $block['title'] );
+		$content .= $block['content'];
+	}
+
+	return $content;
+}
+
+/**
+ * Creates a reusable block with a video.
+ *
+ * Reusable blocks are stored in custom post types.
+ * This creates one, and returns the ID on success.
+ *
+ * @return int|\WP_Error $post_id The post ID where the reusable block is stored, and 0 or WP_Error in case of failure.
+ */
+function create_test_reusable_block() {
+	return wp_insert_post( array(
+		'post_type'    => 'wp_block',
+		'post_title'   => 'Test Reusable Block',
+		'post_content' => '<!-- wp:core/video --><figure class="wp-block-video"><video src="https://videos.files.wordpress.com/DK5mLrbr/video-ca6dc0ab4a_hd.mp4" controls=""></video></figure><!-- /wp:core/video -->',
+		'post_status'  => 'publish',
+	) );
+}
+
+/**
+ * Creates a Gutenberg test post (page).
+ *
+ * @throws \Exception If there is an error in creating the test page.
+ * @param string $content The content to add to the post.
+ * @return int Page ID.
+ */
+function create_gutenberg_test_post( $content ) {
+	$slug            = 'amp-test-gutenberg-blocks';
+	$title           = 'AMP Test Gutenberg Blocks';
+	$page            = get_page_by_path( "/{$slug}/" );
+	$failure_message = 'The test page could not be added, please try again.';
+	if ( $page ) {
+		$page_id = $page->ID;
+	} else {
+		$page_id = wp_insert_post( array(
+			'post_name'  => $slug,
+			'post_title' => $title,
+			'post_type'  => 'page',
+		) );
+
+		if ( ! $page_id || is_wp_error( $page_id ) ) {
+			throw new \Exception( $failure_message );
+		}
+	}
+
+	$update = wp_update_post( array(
+		'ID'           => $page_id,
+		'post_content' => $content,
+	) );
+
+	if ( ! $update ) {
+		throw new \Exception( $failure_message );
+	}
+	return $update;
+}
+
+// Bootstrap.
+if ( defined( 'WP_CLI' ) ) {
+	try {
+		$post_id = create_gutenberg_test_post( get_test_block_fixtures() );
+		\WP_CLI::success( sprintf( 'The test page is at: %s', \amp_get_permalink( $post_id ) . '#development=1' ) );
+	} catch ( \Exception $e ) {
+		\WP_CLI::error( $e->getMessage() );
+	}
+} else {
+	echo "This script should be run WP-CLI via: wp eval-file bin/create-gutenberg-test-post.php\n";
+	exit( 1 );
+}
diff --git a/bin/create-gutenberg-test-post.sh b/bin/create-gutenberg-test-post.sh
new file mode 100644
index 00000000000..1c719dac00c
--- /dev/null
+++ b/bin/create-gutenberg-test-post.sh
@@ -0,0 +1,32 @@
+#!/bin/bash
+set -e
+cd "$(dirname "$0")"
+
+BIN_PATH="$(pwd)"
+PROJECT_PATH=$(dirname $PWD)
+PLUGINS_PATH=$(dirname $PROJECT_PATH)
+GUTENBERG_PATH=$PLUGINS_PATH/gutenberg
+
+# Clone the Gutenberg plugin, or pull the master branch if it's already present.
+if [[ ! -e $GUTENBERG_PATH ]]; then
+	cd $PLUGINS_PATH
+	echo "This needs to clone the Gutenberg plugin into your plugins directory, as it looks like it's not there."
+	read -p "Is that alright? y/n " -r
+	if [[ $REPLY =~ [Yy] ]]; then
+		git clone https://github.com/WordPress/gutenberg.git
+		wp plugin activate gutenberg
+		echo "The Gutenberg plugin is cloned. Please follow the build steps:"
+		echo "https://github.com/WordPress/gutenberg/blob/master/CONTRIBUTING.md"
+	else
+		echo "Exiting script."
+		exit 1
+	fi
+else
+	cd $GUTENBERG_PATH
+	if [ 'master' == $( git rev-parse --abbrev-ref HEAD ) ]; then
+		git pull origin master
+	fi
+fi
+
+cd $PROJECT_PATH
+wp eval-file bin/create-gutenberg-test-post.php
diff --git a/bin/deploy-travis-pantheon.sh b/bin/deploy-travis-pantheon.sh
new file mode 100755
index 00000000000..3d84d8e6e45
--- /dev/null
+++ b/bin/deploy-travis-pantheon.sh
@@ -0,0 +1,99 @@
+#!/bin/bash
+set -e
+# Travis CI Deploy script to Pantheon
+
+# Positional args:
+pantheon_site=$1
+pantheon_uuid=$2
+ssh_identity=$3
+pantheon_branch=$4
+
+if [[ -z "$pantheon_site" ]]; then
+    echo "Missing pantheon_site positional arg 1"
+    exit 1
+fi
+if [[ -z "$pantheon_uuid" ]]; then
+    echo "Missing pantheon_uuid positional arg 2"
+    exit 1
+fi
+if [[ -z "$ssh_identity" ]]; then
+    echo "Missing ssh_identity positional arg 3"
+    exit 1
+fi
+if [[ -z "$pantheon_branch" ]]; then
+    echo "Missing pantheon_branch positional arg 4"
+    exit 1
+fi
+
+cd "$(dirname "$0")/.."
+project_dir="$(pwd)"
+repo_dir="$HOME/deployment-targets/$pantheon_site"
+
+# Restrict deploys to commits pushed to a branch name that can be used as a subdomain, specifically here on a Pantheon multidev environment:
+# "Branch names can contain any ASCII letter and number (a through z, 0 through 9) and hyphen (dash). The branch name must start with a letter or number.
+# Currently, the maximum length is 11 characters and environments cannot be created with the following reserved names."
+# Note: master is allowed since it maps to dev; the dev branch is instead disallowed.
+if ! [[ $pantheon_branch =~ ^[a-z][a-z0-9-]{0,10}$ ]] || [[ $pantheon_branch =~ ^(live|test|dev|settings|team|support|debug|multidev|files|tags|billing)$ ]]; then
+    echo "Aborting since branch '$pantheon_branch' cannot be an environment."
+    exit 1
+fi
+
+ssh-add $ssh_identity
+
+if ! grep -q "codeserver.dev.$pantheon_uuid.drush.in" ~/.ssh/known_hosts; then
+    ssh-keyscan -p 2222 codeserver.dev.$pantheon_uuid.drush.in >> ~/.ssh/known_hosts
+fi
+
+if ! grep -q "codeserver.dev.$pantheon_uuid.drush.in" ~/.ssh/config; then
+    echo "Host $pantheon_site" >> ~/.ssh/config
+    echo "  Hostname codeserver.dev.$pantheon_uuid.drush.in" >> ~/.ssh/config
+    echo "  User codeserver.dev.$pantheon_uuid" >> ~/.ssh/config
+    echo "  IdentityFile $ssh_identity" >> ~/.ssh/config
+    echo "  IdentitiesOnly yes" >> ~/.ssh/config
+    echo "  Port 2222" >> ~/.ssh/config
+    echo "  KbdInteractiveAuthentication no" >> ~/.ssh/config
+fi
+git config --global user.name "Travis CI"
+git config --global user.email "travis-ci+$pantheon_site@xwp.co"
+
+# Set the branch.
+if [[ $pantheon_branch == 'master' ]]; then
+    pantheon_env=dev
+else
+    pantheon_env=$pantheon_branch
+fi
+
+if [ ! -e "$repo_dir/.git" ]; then
+    git clone -v ssh://codeserver.dev.$pantheon_uuid@codeserver.dev.$pantheon_uuid.drush.in:2222/~/repository.git "$repo_dir"
+fi
+
+cd "$repo_dir"
+git fetch
+
+if git rev-parse --verify --quiet "$pantheon_branch" > /dev/null; then
+    git checkout "$pantheon_branch"
+else
+    git checkout -b "$pantheon_branch"
+fi
+if git rev-parse --verify --quiet "origin/$pantheon_branch" > /dev/null; then
+    git reset --hard "origin/$pantheon_branch"
+fi
+
+# Install and build.
+cd "$project_dir"
+if [ ! -e node_modules/.bin ]; then
+    npm install
+fi
+PATH="node_modules/.bin/:$PATH"
+grunt build
+rsync -avz --delete ./build/ "$repo_dir/wp-content/plugins/amp/"
+git --no-pager log -1 --format="Build AMP plugin at %h: %s" > /tmp/commit-message.txt
+
+# Commit and deploy.
+cd "$repo_dir"
+git add -A "wp-content/plugins/amp/"
+git commit -F /tmp/commit-message.txt
+git push origin $pantheon_branch
+
+echo "View site at http://$pantheon_env-$pantheon_site.pantheonsite.io/"
+echo "Access Pantheon dashboard at https://dashboard.pantheon.io/sites/$pantheon_uuid#$pantheon_env"
diff --git a/bin/keys/id_rsa_ampconfdemo.enc b/bin/keys/id_rsa_ampconfdemo.enc
new file mode 100644
index 00000000000..807047641ec
Binary files /dev/null and b/bin/keys/id_rsa_ampconfdemo.enc differ
diff --git a/bin/keys/id_rsa_ampconfdemo.pub b/bin/keys/id_rsa_ampconfdemo.pub
new file mode 100644
index 00000000000..153effc4fe7
--- /dev/null
+++ b/bin/keys/id_rsa_ampconfdemo.pub
@@ -0,0 +1 @@
+ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDKI5pL/0+v6neXAyIAy9nCrFQS4g4YoeNe7Ij+2wzgO5tZ1wnY931pm5IJ4JD310m/LYqpVn6Uwc/qKwVDeHHPQDOAuL7eCJIt2ns+DqYoP1VEYBYgeyOdc8j20n0doi5fYklc6CYWHVJomvQ/Sn5ACfnuA4ppBZdUxIo70tJzv7SAyOZli4D7hNhxpBNl4i9H0S/XIT61TSroEAFU78BR1hv9e+U0SkGSpIP44vuwQ7jG/DlB0X7J2p1w9VosnEcwbDaMJF4THiSDUAB6Ezwxa481vKPHFunGnwuOl7QSbglz/WrZ1/v5N8Uzz2E6moRT1fMgBC2ygWJAgwq3VS/b travis-ci+ampconfdemo@xwp.co
diff --git a/bin/verify-version-consistency.php b/bin/verify-version-consistency.php
index 4a42d2fcb9f..1c9b8328fee 100755
--- a/bin/verify-version-consistency.php
+++ b/bin/verify-version-consistency.php
@@ -1,4 +1,4 @@
-#!/usr/bin/env
+#!/usr/bin/env php
 <?php
 /**
  * Verify versions referenced in plugin match.
@@ -39,7 +39,7 @@
 $versions['readme.md#changelog'] = $matches['version'];
 
 $plugin_file = file_get_contents( dirname( __FILE__ ) . '/../amp.php' );
-if ( ! preg_match( '/\*\s*Version:\s*(?P<version>\d+\.\d+(?:.\d+)?)/', $plugin_file, $matches ) ) {
+if ( ! preg_match( '/\*\s*Version:\s*(?P<version>\d+\.\d+(?:.\d+)?(-\w+)?)/', $plugin_file, $matches ) ) {
 	echo "Could not find version in readme metadata\n";
 	exit( 1 );
 }
@@ -59,3 +59,8 @@
 	fwrite( STDERR, "Error: Not all version references have been updated.\n" );
 	exit( 1 );
 }
+
+if ( false === strpos( $versions['amp.php#metadata'], '-' ) && ! preg_match( '/^\d+\.\d+\.\d+$/', $versions['amp.php#metadata'] ) ) {
+	fwrite( STDERR, sprintf( "Error: Release version (%s) lacks patch number. For new point releases, supply patch number of 0, such as 0.9.0 instead of 0.9.\n", $versions['amp.php#metadata'] ) );
+	exit( 1 );
+}
diff --git a/contributing.md b/contributing.md
index 9b7c8c29830..ba5f791c223 100644
--- a/contributing.md
+++ b/contributing.md
@@ -42,6 +42,14 @@ To run it:
 3. run `wp eval-file bin/create-comments-on-test-post.php`
 4. go to the URL that is output in the command line
 
+## Testing Gutenberg Block Support
+
+The following script creates a post with all core Gutenberg blocks. To run it:
+1. `ssh` into an environment like [VVV](https://github.com/Varying-Vagrant-Vagrants/VVV)
+2. `cd` to the root of this plugin
+3. run `bash bin/create-gutenberge-test-post.sh`
+4. go to the URL that is output in the command line
+
 ## PHPUnit Testing
 
 Please run these tests in an environment with WordPress unit tests installed, like [VVV](https://github.com/Varying-Vagrant-Vagrants/VVV).
diff --git a/dev-lib b/dev-lib
index 4ac4bd20b5a..c80f10dad3c 160000
--- a/dev-lib
+++ b/dev-lib
@@ -1 +1 @@
-Subproject commit 4ac4bd20b5a4b3953eb81a8d2536baef2bf60dcb
+Subproject commit c80f10dad3cb402213914438d8ae1cdeccce9e4a
diff --git a/includes/admin/class-amp-customizer.php b/includes/admin/class-amp-customizer.php
index a3efe74c55e..cfb7bb30fc6 100644
--- a/includes/admin/class-amp-customizer.php
+++ b/includes/admin/class-amp-customizer.php
@@ -134,7 +134,7 @@ public function add_customizer_scripts() {
 
 		wp_add_inline_script( 'amp-customize-controls', sprintf( 'ampCustomizeControls.boot( %s );',
 			wp_json_encode( array(
-				'queryVar' => AMP_QUERY_VAR,
+				'queryVar' => amp_get_slug(),
 				'panelId'  => self::PANEL_ID,
 				'ampUrl'   => amp_admin_get_preview_permalink(),
 				'l10n'     => array(
diff --git a/includes/admin/class-amp-post-meta-box.php b/includes/admin/class-amp-post-meta-box.php
index 1152c4db1a3..55842b335ba 100644
--- a/includes/admin/class-amp-post-meta-box.php
+++ b/includes/admin/class-amp-post-meta-box.php
@@ -121,6 +121,8 @@ public function enqueue_admin_assets() {
 			isset( $screen->base )
 			&&
 			'post' === $screen->base
+			&&
+			is_post_type_viewable( $post->post_type )
 		);
 		if ( ! $validate ) {
 			return;
@@ -143,7 +145,7 @@ public function enqueue_admin_assets() {
 		);
 		wp_add_inline_script( self::ASSETS_HANDLE, sprintf( 'ampPostMetaBox.boot( %s );',
 			wp_json_encode( array(
-				'previewLink'     => esc_url_raw( add_query_arg( AMP_QUERY_VAR, '', get_preview_post_link( $post ) ) ),
+				'previewLink'     => esc_url_raw( add_query_arg( amp_get_slug(), '', get_preview_post_link( $post ) ) ),
 				'canonical'       => amp_is_canonical(),
 				'enabled'         => post_supports_amp( $post ),
 				'canSupport'      => count( AMP_Post_Type_Support::get_support_errors( $post ) ) === 0,
@@ -165,6 +167,8 @@ public function render_status( $post ) {
 		$verify = (
 			isset( $post->ID )
 			&&
+			is_post_type_viewable( $post->post_type )
+			&&
 			current_user_can( 'edit_post', $post->ID )
 			&&
 			! amp_is_canonical()
@@ -233,7 +237,7 @@ public function preview_post_link( $link ) {
 		);
 
 		if ( $is_amp ) {
-			$link = add_query_arg( AMP_QUERY_VAR, true, $link );
+			$link = add_query_arg( amp_get_slug(), true, $link );
 		}
 
 		return $link;
diff --git a/includes/admin/functions.php b/includes/admin/functions.php
index f5539a05a04..80b94511e3d 100644
--- a/includes/admin/functions.php
+++ b/includes/admin/functions.php
@@ -48,7 +48,7 @@ function amp_admin_get_preview_permalink() {
 	 */
 	$post_type = (string) apply_filters( 'amp_customizer_post_type', 'post' );
 
-	if ( ! post_type_supports( $post_type, AMP_QUERY_VAR ) ) {
+	if ( ! post_type_supports( $post_type, amp_get_slug() ) ) {
 		return null;
 	}
 
diff --git a/includes/amp-frontend-actions.php b/includes/amp-frontend-actions.php
index f62b93f6b70..f5d7ebca13d 100644
--- a/includes/amp-frontend-actions.php
+++ b/includes/amp-frontend-actions.php
@@ -10,23 +10,31 @@
 /**
  * Add amphtml link to frontend.
  *
+ * @todo This function's name is incorrect. It's not about adding a canonical link but adding the amphtml link.
+ *
  * @since 0.2
  */
 function amp_frontend_add_canonical() {
 
-	// Prevent showing amphtml link if theme supports AMP but paired mode is not available.
-	if ( current_theme_supports( 'amp' ) && ! AMP_Theme_Support::is_paired_available() ) {
-		return;
-	}
-
 	/**
 	 * Filters whether to show the amphtml link on the frontend.
 	 *
+	 * @todo This filter's name is incorrect. It's not about adding a canonical link but adding the amphtml link.
 	 * @since 0.2
 	 */
 	if ( false === apply_filters( 'amp_frontend_show_canonical', true ) ) {
 		return;
 	}
 
-	printf( '<link rel="amphtml" href="%s">', esc_url( amp_get_permalink( get_queried_object_id() ) ) );
+	$amp_url = null;
+	if ( is_singular() ) {
+		$amp_url = amp_get_permalink( get_queried_object_id() );
+	} elseif ( isset( $_SERVER['REQUEST_URI'] ) ) {
+		$host_url = preg_replace( '#(^https?://[^/]+)/.*#', '$1', home_url( '/' ) );
+		$self_url = esc_url_raw( $host_url . wp_unslash( $_SERVER['REQUEST_URI'] ) );
+		$amp_url  = add_query_arg( amp_get_slug(), '', $self_url );
+	}
+	if ( $amp_url ) {
+		printf( '<link rel="amphtml" href="%s">', esc_url( $amp_url ) );
+	}
 }
diff --git a/includes/amp-helper-functions.php b/includes/amp-helper-functions.php
index d8c4690568c..27d27696058 100644
--- a/includes/amp-helper-functions.php
+++ b/includes/amp-helper-functions.php
@@ -5,6 +5,36 @@
  * @package AMP
  */
 
+/**
+ * Get the slug used in AMP for the query var, endpoint, and post type support.
+ *
+ * The return value can be overridden by previously defining a AMP_QUERY_VAR
+ * constant or by adding a 'amp_query_var' filter, but *warning* this ability
+ * may be deprecated in the future. Normally the slug should be just 'amp'.
+ *
+ * @since 0.7
+ * @return string Slug used for query var, endpoint, and post type support.
+ */
+function amp_get_slug() {
+	if ( defined( 'AMP_QUERY_VAR' ) ) {
+		return AMP_QUERY_VAR;
+	}
+
+	/**
+	 * Filter the AMP query variable.
+	 *
+	 * Warning: This filter may become deprecated.
+	 *
+	 * @since 0.3.2
+	 * @param string $query_var The AMP query variable.
+	 */
+	$query_var = apply_filters( 'amp_query_var', 'amp' );
+
+	define( 'AMP_QUERY_VAR', $query_var );
+
+	return $query_var;
+}
+
 /**
  * Retrieves the full AMP-specific permalink for the given post ID.
  *
@@ -32,12 +62,16 @@ function amp_get_permalink( $post_id ) {
 		return $pre_url;
 	}
 
-	$parsed_url = wp_parse_url( get_permalink( $post_id ) );
-	$structure  = get_option( 'permalink_structure' );
-	if ( empty( $structure ) || ! empty( $parsed_url['query'] ) || is_post_type_hierarchical( get_post_type( $post_id ) ) ) {
-		$amp_url = add_query_arg( AMP_QUERY_VAR, '', get_permalink( $post_id ) );
+	if ( amp_is_canonical() ) {
+		$amp_url = get_permalink( $post_id );
 	} else {
-		$amp_url = trailingslashit( get_permalink( $post_id ) ) . user_trailingslashit( AMP_QUERY_VAR, 'single_amp' );
+		$parsed_url = wp_parse_url( get_permalink( $post_id ) );
+		$structure  = get_option( 'permalink_structure' );
+		if ( empty( $structure ) || ! empty( $parsed_url['query'] ) || is_post_type_hierarchical( get_post_type( $post_id ) ) ) {
+			$amp_url = add_query_arg( amp_get_slug(), '', get_permalink( $post_id ) );
+		} else {
+			$amp_url = trailingslashit( get_permalink( $post_id ) ) . user_trailingslashit( amp_get_slug(), 'single_amp' );
+		}
 	}
 
 	/**
@@ -51,6 +85,25 @@ function amp_get_permalink( $post_id ) {
 	return apply_filters( 'amp_get_permalink', $amp_url, $post_id );
 }
 
+/**
+ * Remove the AMP endpoint (and query var) from a given URL.
+ *
+ * @since 0.7
+ *
+ * @param string $url URL.
+ * @return string URL with AMP stripped.
+ */
+function amp_remove_endpoint( $url ) {
+
+	// Strip endpoint.
+	$url = preg_replace( ':/' . preg_quote( amp_get_slug(), ':' ) . '(?=/?(\?|#|$)):', '', $url );
+
+	// Strip query var.
+	$url = remove_query_arg( amp_get_slug(), $url );
+
+	return $url;
+}
+
 /**
  * Determine whether a given post supports AMP.
  *
@@ -118,6 +171,10 @@ function post_supports_amp( $post ) {
  * @return bool Whether it is the AMP endpoint.
  */
 function is_amp_endpoint() {
+	if ( is_admin() || is_feed() || ( defined( 'REST_REQUEST' ) && REST_REQUEST ) ) {
+		return false;
+	}
+
 	if ( amp_is_canonical() ) {
 		return true;
 	}
@@ -126,7 +183,7 @@ function is_amp_endpoint() {
 		_doing_it_wrong( __FUNCTION__, sprintf( esc_html__( "is_amp_endpoint() was called before the 'parse_query' hook was called. This function will always return 'false' before the 'parse_query' hook is called.", 'amp' ) ), '0.4.2' );
 	}
 
-	return false !== get_query_var( AMP_QUERY_VAR, false );
+	return false !== get_query_var( amp_get_slug(), false );
 }
 
 /**
@@ -144,6 +201,7 @@ function amp_get_asset_url( $file ) {
  *
  * @since 0.7
  * @link https://www.ampproject.org/docs/reference/spec#boilerplate
+ *
  * @return string Boilerplate code.
  */
 function amp_get_boilerplate_code() {
@@ -151,6 +209,127 @@ function amp_get_boilerplate_code() {
 		. '<noscript><style amp-boilerplate>body{-webkit-animation:none;-moz-animation:none;-ms-animation:none;animation:none}</style></noscript>';
 }
 
+/**
+ * Register default scripts for AMP components.
+ *
+ * @param WP_Scripts $wp_scripts Scripts.
+ */
+function amp_register_default_scripts( $wp_scripts ) {
+
+	// AMP Runtime.
+	$handle = 'amp-runtime';
+	$wp_scripts->add(
+		$handle,
+		'https://cdn.ampproject.org/v0.js',
+		array(),
+		null
+	);
+	$wp_scripts->add_data( $handle, 'amp_script_attributes', array(
+		'async' => true,
+	) );
+
+	// Shadow AMP API.
+	$handle = 'amp-shadow';
+	$wp_scripts->add(
+		$handle,
+		'https://cdn.ampproject.org/shadow-v0.js',
+		array(),
+		null
+	);
+	$wp_scripts->add_data( $handle, 'amp_script_attributes', array(
+		'async' => true,
+	) );
+
+	// Get all AMP components as defined in the spec.
+	$extensions = array();
+	foreach ( AMP_Allowed_Tags_Generated::get_allowed_tags() as $allowed_tag ) {
+		foreach ( $allowed_tag as $rule_spec ) {
+			if ( ! empty( $rule_spec[ AMP_Rule_Spec::TAG_SPEC ]['requires_extension'] ) ) {
+				$extensions = array_merge(
+					$extensions,
+					$rule_spec[ AMP_Rule_Spec::TAG_SPEC ]['requires_extension']
+				);
+			}
+		}
+	}
+	$extensions = array_unique( $extensions );
+
+	foreach ( $extensions as $extension ) {
+		$src = sprintf(
+			'https://cdn.ampproject.org/v0/%s-%s.js',
+			$extension,
+			'latest'
+		);
+
+		$wp_scripts->add(
+			$extension,
+			$src,
+			array( 'amp-runtime' ),
+			null
+		);
+	}
+}
+
+/**
+ * Add AMP script attributes to enqueued scripts.
+ *
+ * @link https://core.trac.wordpress.org/ticket/12009
+ * @since 0.7
+ *
+ * @param string $tag    The script tag.
+ * @param string $handle The script handle.
+ * @return string Script loader tag.
+ */
+function amp_filter_script_loader_tag( $tag, $handle ) {
+	$prefix = 'https://cdn.ampproject.org/';
+	$src    = wp_scripts()->registered[ $handle ]->src;
+	if ( 0 !== strpos( $src, $prefix ) ) {
+		return $tag;
+	}
+
+	/*
+	 * All scripts from AMP CDN should be loaded async.
+	 * See <https://www.ampproject.org/docs/integration/pwa-amp/amp-in-pwa#include-"shadow-amp"-in-your-progressive-web-app>.
+	 */
+	$attributes = array(
+		'async' => true,
+	);
+
+	// Add custom-template and custom-element attributes. All component scripts look like https://cdn.ampproject.org/v0/:name-:version.js.
+	if ( 'v0' === strtok( substr( $src, strlen( $prefix ) ), '/' ) ) {
+		/*
+		 * Per the spec, "Most extensions are custom-elements." In fact, there is only one custom template. So we hard-code it here.
+		 *
+		 * @link https://github.com/ampproject/amphtml/blob/cd685d4e62153557519553ffa2183aedf8c93d62/validator/validator.proto#L326-L328
+		 * @link https://github.com/ampproject/amphtml/blob/cd685d4e62153557519553ffa2183aedf8c93d62/extensions/amp-mustache/validator-amp-mustache.protoascii#L27
+		 */
+		if ( 'amp-mustache' === $handle ) {
+			$attributes['custom-template'] = $handle;
+		} else {
+			$attributes['custom-element'] = $handle;
+		}
+	}
+
+	// Add each attribute (if it hasn't already been added).
+	foreach ( $attributes as $key => $value ) {
+		if ( ! preg_match( ":\s$key(=|>|\s):", $tag ) ) {
+			if ( true === $value ) {
+				$attribute_string = sprintf( ' %s', esc_attr( $key ) );
+			} else {
+				$attribute_string = sprintf( ' %s="%s"', esc_attr( $key ), esc_attr( $value ) );
+			}
+			$tag = preg_replace(
+				':(?=></script>):',
+				$attribute_string,
+				$tag,
+				1
+			);
+		}
+	}
+
+	return $tag;
+}
+
 /**
  * Retrieve analytics data added in backend.
  *
@@ -194,9 +373,12 @@ function amp_get_analytics( $analytics = array() ) {
  *
  * @since 0.7
  *
- * @param array $analytics Analytics entries.
+ * @param array|string $analytics Analytics entries, or empty string when called via wp_footer action.
  */
 function amp_print_analytics( $analytics ) {
+	if ( '' === $analytics ) {
+		$analytics = array();
+	}
 	$analytics_entries = amp_get_analytics( $analytics );
 
 	if ( empty( $analytics_entries ) ) {
@@ -260,6 +442,7 @@ function amp_get_content_embed_handlers( $post = null ) {
 			'AMP_Vine_Embed_Handler'        => array(),
 			'AMP_Facebook_Embed_Handler'    => array(),
 			'AMP_Pinterest_Embed_Handler'   => array(),
+			'AMP_Playlist_Embed_Handler'    => array(),
 			'AMP_Reddit_Embed_Handler'      => array(),
 			'AMP_Tumblr_Embed_Handler'      => array(),
 			'AMP_Gallery_Embed_Handler'     => array(),
@@ -483,94 +666,3 @@ function amp_print_schemaorg_metadata() {
 	<script type="application/ld+json"><?php echo wp_json_encode( $metadata ); ?></script>
 	<?php
 }
-
-/**
- * Hook into a form submissions, such as comment the form or some other .
- *
- * @since 0.7.0
- * @global string $pagenow
- */
-function amp_handle_xhr_request() {
-	global $pagenow;
-	if ( ! isset( $_GET['__amp_source_origin'] ) ) { // WPCS: CSRF ok. Beware of AMP_Theme_Support::purge_amp_query_vars().
-		return;
-	}
-
-	if ( isset( $pagenow ) && 'wp-comments-post.php' === $pagenow ) {
-		// We don't need any data, so just send a success.
-		add_filter( 'comment_post_redirect', function() {
-			// We don't need any data, so just send a success.
-			wp_send_json_success();
-		}, PHP_INT_MAX, 2 );
-		amp_handle_xhr_headers_output();
-	} elseif ( isset( $_GET['_wp_amp_action_xhr_converted'] ) ) { // WPCS: CSRF ok.
-		add_filter( 'wp_redirect', 'amp_intercept_post_request_redirect', PHP_INT_MAX, 2 );
-		amp_handle_xhr_headers_output();
-	}
-}
-
-/**
- * Handle the AMP XHR headers and output errors.
- *
- * @since 0.7.0
- */
-function amp_handle_xhr_headers_output() {
-	// Add die handler for AMP error display.
-	add_filter( 'wp_die_handler', function() {
-		/**
-		 * New error handler for AMP form submission.
-		 *
-		 * @param WP_Error|string $error The error to handle.
-		 */
-		return function( $error ) {
-			status_header( 400 );
-			if ( is_wp_error( $error ) ) {
-				$error = $error->get_error_message();
-			}
-			$amp_mustache_allowed_html_tags = array( 'strong', 'b', 'em', 'i', 'u', 's', 'small', 'mark', 'del', 'ins', 'sup', 'sub' );
-			wp_send_json( array(
-				'error' => wp_kses( $error, array_fill_keys( $amp_mustache_allowed_html_tags, array() ) ),
-			) );
-		};
-	} );
-
-	// Send AMP header.
-	$origin = esc_url_raw( wp_unslash( $_GET['__amp_source_origin'] ) ); // WPCS: CSRF ok.
-	header( 'AMP-Access-Control-Allow-Source-Origin: ' . $origin, true );
-}
-
-/**
- * Intercept the response to a non-comment POST request.
- *
- * @since 0.7.0
- * @param string $location The location to redirect to.
- */
-function amp_intercept_post_request_redirect( $location ) {
-
-	// Make sure relative redirects get made absolute.
-	$parsed_location = array_merge(
-		array(
-			'scheme' => 'https',
-			'host'   => wp_parse_url( home_url(), PHP_URL_HOST ),
-			'path'   => strtok( wp_unslash( $_SERVER['REQUEST_URI'] ), '?' ),
-		),
-		wp_parse_url( $location )
-	);
-
-	$absolute_location = $parsed_location['scheme'] . '://' . $parsed_location['host'];
-	if ( isset( $parsed_location['port'] ) ) {
-		$absolute_location .= ':' . $parsed_location['port'];
-	}
-	$absolute_location .= $parsed_location['path'];
-	if ( isset( $parsed_location['query'] ) ) {
-		$absolute_location .= '?' . $parsed_location['query'];
-	}
-	if ( isset( $parsed_location['fragment'] ) ) {
-		$absolute_location .= '#' . $parsed_location['fragment'];
-	}
-
-	header( 'AMP-Redirect-To: ' . $absolute_location );
-	header( 'Access-Control-Expose-Headers: AMP-Redirect-To' );
-	// Send json success as no data is required.
-	wp_send_json_success();
-}
diff --git a/includes/amp-post-template-actions.php b/includes/amp-post-template-actions.php
index c33835a65dc..b956faaf6c6 100644
--- a/includes/amp-post-template-actions.php
+++ b/includes/amp-post-template-actions.php
@@ -46,23 +46,27 @@ function amp_post_template_add_canonical( $amp_template ) {
 /**
  * Print scripts.
  *
+ * @see amp_register_default_scripts()
+ * @see amp_filter_script_loader_tag()
  * @param AMP_Post_Template $amp_template Template.
  */
 function amp_post_template_add_scripts( $amp_template ) {
+
+	// Just in case the runtime has been overridden by amp_post_template_data filter.
+	wp_scripts()->registered['amp-runtime']->src = $amp_template->get( 'amp_runtime_script' );
+
+	// Make sure any filtered extension script URLs get updated in registered scripts before printing.
 	$scripts = $amp_template->get( 'amp_component_scripts', array() );
-	foreach ( $scripts as $element => $script ) {
-		$custom_type = ( 'amp-mustache' === $element ) ? 'template' : 'element';
-		printf(
-			'<script custom-%s="%s" src="%s" async></script>', // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
-			esc_attr( $custom_type ),
-			esc_attr( $element ),
-			esc_url( $script )
-		);
+	foreach ( $scripts as $handle => $value ) {
+		if ( is_string( $value ) && wp_script_is( $handle, 'registered' ) ) {
+			wp_scripts()->registered[ $handle ]->src = $value;
+		}
 	}
-	printf(
-		'<script src="%s" async></script>', // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
-		esc_url( $amp_template->get( 'amp_runtime_script' ) )
-	);
+
+	wp_print_scripts( array_merge(
+		array( 'amp-runtime' ),
+		array_keys( $scripts )
+	) );
 }
 
 /**
diff --git a/includes/class-amp-autoloader.php b/includes/class-amp-autoloader.php
index 7bf991c8d54..3ec923b7bde 100644
--- a/includes/class-amp-autoloader.php
+++ b/includes/class-amp-autoloader.php
@@ -42,6 +42,7 @@ class AMP_Autoloader {
 		'AMP_Issuu_Embed_Handler'                     => 'includes/embeds/class-amp-issuu-embed-handler',
 		'AMP_Meetup_Embed_Handler'                    => 'includes/embeds/class-amp-meetup-embed-handler',
 		'AMP_Pinterest_Embed_Handler'                 => 'includes/embeds/class-amp-pinterest-embed',
+		'AMP_Playlist_Embed_Handler'                  => 'includes/embeds/class-amp-playlist-embed-handler',
 		'AMP_Reddit_Embed_Handler'                    => 'includes/embeds/class-amp-reddit-embed-handler',
 		'AMP_SoundCloud_Embed_Handler'                => 'includes/embeds/class-amp-soundcloud-embed',
 		'AMP_Tumblr_Embed_Handler'                    => 'includes/embeds/class-amp-tumblr-embed-handler',
diff --git a/includes/class-amp-post-type-support.php b/includes/class-amp-post-type-support.php
index dfe1e0496d4..22a1bef580b 100644
--- a/includes/class-amp-post-type-support.php
+++ b/includes/class-amp-post-type-support.php
@@ -54,7 +54,7 @@ public static function add_post_type_support() {
 			AMP_Options_Manager::get_option( 'supported_post_types', array() )
 		);
 		foreach ( $post_types as $post_type ) {
-			add_post_type_support( $post_type, AMP_QUERY_VAR );
+			add_post_type_support( $post_type, amp_get_slug() );
 		}
 	}
 
@@ -73,7 +73,7 @@ public static function get_support_errors( $post ) {
 		$errors = array();
 
 		// Because `add_rewrite_endpoint` doesn't let us target specific post_types.
-		if ( isset( $post->post_type ) && ! post_type_supports( $post->post_type, AMP_QUERY_VAR ) ) {
+		if ( isset( $post->post_type ) && ! post_type_supports( $post->post_type, amp_get_slug() ) ) {
 			$errors[] = 'post-type-support';
 		}
 
diff --git a/includes/class-amp-theme-support.php b/includes/class-amp-theme-support.php
index acda180917f..bef0df4d80a 100644
--- a/includes/class-amp-theme-support.php
+++ b/includes/class-amp-theme-support.php
@@ -67,10 +67,34 @@ class AMP_Theme_Support {
 	 */
 	public static $purged_amp_query_vars = array();
 
+	/**
+	 * Headers sent (or attempted to be sent).
+	 *
+	 * @since 0.7
+	 * @see AMP_Theme_Support::send_header()
+	 * @var array[]
+	 */
+	public static $headers_sent = array();
+
+	/**
+	 * Output buffering level when starting.
+	 *
+	 * @since 0.7
+	 * @var int
+	 */
+	protected static $initial_ob_level = 0;
+
 	/**
 	 * Initialize.
 	 */
 	public static function init() {
+		if ( ! current_theme_supports( 'amp' ) ) {
+			return;
+		}
+
+		self::purge_amp_query_vars();
+		self::handle_xhr_request();
+
 		require_once AMP__DIR__ . '/includes/amp-post-template-actions.php';
 
 		// Validate theme support usage.
@@ -79,26 +103,66 @@ public static function init() {
 			$args = array_shift( $support );
 			if ( ! is_array( $args ) ) {
 				trigger_error( esc_html__( 'Expected AMP theme support arg to be array.', 'amp' ) ); // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_trigger_error
-			} elseif ( count( array_diff( array_keys( $args ), array( 'template_dir', 'available_callback' ) ) ) !== 0 ) {
+			} elseif ( count( array_diff( array_keys( $args ), array( 'template_dir', 'available_callback', 'comments_live_list' ) ) ) !== 0 ) {
 				trigger_error( esc_html__( 'Expected AMP theme support to only have template_dir and/or available_callback.', 'amp' ) ); // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_trigger_error
 			}
 		}
 
-		if ( amp_is_canonical() ) {
+		add_action( 'widgets_init', array( __CLASS__, 'register_widgets' ) );
+
+		/*
+		 * Note that wp action is use instead of template_redirect because some themes/plugins output
+		 * the response at this action and then short-circuit with exit. So this is why the the preceding
+		 * action to template_redirect--the wp action--is used instead.
+		 */
+		add_action( 'wp', array( __CLASS__, 'finish_init' ), PHP_INT_MAX );
+	}
 
-			// Redirect to canonical URL if the AMP URL was loaded, since canonical is now AMP.
-			if ( false !== get_query_var( AMP_QUERY_VAR, false ) ) { // Because is_amp_endpoint() now returns true if amp_is_canonical().
-				wp_safe_redirect( self::get_current_canonical_url(), 302 ); // Temporary redirect because canonical may change in future.
-				exit;
+	/**
+	 * Finish initialization once query vars are set.
+	 *
+	 * @since 0.7
+	 */
+	public static function finish_init() {
+		if ( ! is_amp_endpoint() ) {
+			// Add amphtml link when paired mode is available.
+			if ( self::is_paired_available() ) {
+				amp_add_frontend_actions(); // @todo This function is poor in how it requires a file that then does add_action().
+				if ( ! has_action( 'wp_head', 'amp_frontend_add_canonical' ) ) {
+					add_action( 'wp_head', 'amp_frontend_add_canonical' );
+				}
 			}
+			return;
+		}
+
+		if ( amp_is_canonical() ) {
+			self::redirect_canonical_amp();
 		} else {
 			self::register_paired_hooks();
 		}
 
-		self::purge_amp_query_vars(); // Note that amp_prepare_xhr_post() still looks at $_GET['__amp_source_origin'].
-		self::register_hooks();
-		self::$embed_handlers    = self::register_content_embed_handlers();
+		self::add_hooks();
 		self::$sanitizer_classes = amp_get_content_sanitizers();
+		self::$embed_handlers    = self::register_content_embed_handlers();
+	}
+
+	/**
+	 * Redirect to canonical URL if the AMP URL was loaded, since canonical is now AMP.
+	 *
+	 * @since 0.7
+	 */
+	public static function redirect_canonical_amp() {
+		if ( false !== get_query_var( amp_get_slug(), false ) ) { // Because is_amp_endpoint() now returns true if amp_is_canonical().
+			$url = preg_replace( '#^(https?://.+?)(/.*)$#', '$1', home_url( '/' ) );
+			if ( isset( $_SERVER['REQUEST_URI'] ) ) {
+				$url .= wp_unslash( $_SERVER['REQUEST_URI'] );
+			}
+
+			$url = amp_remove_endpoint( $url );
+
+			wp_safe_redirect( $url, 302 ); // Temporary redirect because canonical may change in future.
+			exit;
+		}
 	}
 
 	/**
@@ -128,6 +192,18 @@ public static function is_paired_available() {
 		return true;
 	}
 
+	/**
+	 * Determine whether the user is in the Customizer preview iframe.
+	 *
+	 * @since 0.7
+	 *
+	 * @return bool Whether in Customizer preview iframe.
+	 */
+	public static function is_customize_preview_iframe() {
+		global $wp_customize;
+		return is_customize_preview() && $wp_customize->get_messenger_channel();
+	}
+
 	/**
 	 * Register hooks for paired mode.
 	 */
@@ -141,14 +217,21 @@ public static function register_paired_hooks() {
 	/**
 	 * Register hooks.
 	 */
-	public static function register_hooks() {
+	public static function add_hooks() {
 
 		// Remove core actions which are invalid AMP.
 		remove_action( 'wp_head', 'wp_post_preview_js', 1 );
 		remove_action( 'wp_head', 'print_emoji_detection_script', 7 );
-		remove_action( 'wp_head', 'wp_print_head_scripts', 9 );
-		remove_action( 'wp_footer', 'wp_print_footer_scripts', 20 );
 		remove_action( 'wp_print_styles', 'print_emoji_styles' );
+		remove_action( 'wp_head', 'wp_oembed_add_host_js' );
+
+		// Prevent MediaElement.js scripts/styles from being enqueued.
+		add_filter( 'wp_video_shortcode_library', function() {
+			return 'amp';
+		} );
+		add_filter( 'wp_audio_shortcode_library', function() {
+			return 'amp';
+		} );
 
 		/*
 		 * Add additional markup required by AMP <https://www.ampproject.org/docs/reference/spec#required-markup>.
@@ -159,10 +242,12 @@ public static function register_hooks() {
 		 * in this case too we should defer to the theme as well to output the meta charset because it is possible the
 		 * install is not on utf-8 and we may need to do a encoding conversion.
 		 */
-		add_action( 'wp_head', array( __CLASS__, 'add_amp_component_scripts' ), 10 );
-		add_action( 'wp_head', array( __CLASS__, 'print_amp_styles' ) );
+		add_action( 'wp_print_styles', array( __CLASS__, 'print_amp_styles' ), 0 ); // Print boilerplate before theme and plugin stylesheets.
 		add_action( 'wp_head', 'amp_add_generator_metadata', 20 );
-		add_action( 'wp_head', 'amp_print_schemaorg_metadata' );
+
+		add_action( 'wp_enqueue_scripts', array( __CLASS__, 'enqueue_assets' ) );
+		add_action( 'wp_enqueue_scripts', array( __CLASS__, 'dequeue_customize_preview_scripts' ), 1000 );
+		add_filter( 'customize_partial_render', array( __CLASS__, 'filter_customize_partial_render' ) );
 
 		add_action( 'wp_footer', 'amp_print_analytics' );
 
@@ -178,11 +263,18 @@ public static function register_hooks() {
 		 */
 		add_action( 'template_redirect', array( __CLASS__, 'start_output_buffering' ), 0 );
 
-		add_filter( 'wp_list_comments_args', array( __CLASS__, 'amp_set_comments_walker' ), PHP_INT_MAX );
+		// Commenting hooks.
+		add_filter( 'wp_list_comments_args', array( __CLASS__, 'set_comments_walker' ), PHP_INT_MAX );
 		add_filter( 'comment_form_defaults', array( __CLASS__, 'filter_comment_form_defaults' ) );
 		add_filter( 'comment_reply_link', array( __CLASS__, 'filter_comment_reply_link' ), 10, 4 );
 		add_filter( 'cancel_comment_reply_link', array( __CLASS__, 'filter_cancel_comment_reply_link' ), 10, 3 );
-		add_action( 'comment_form', array( __CLASS__, 'add_amp_comment_form_templates' ), 100 );
+		add_action( 'comment_form', array( __CLASS__, 'amend_comment_form' ), 100 );
+		remove_action( 'comment_form', 'wp_comment_form_unfiltered_html_nonce' );
+		add_filter( 'wp_kses_allowed_html', array( __CLASS__, 'whitelist_layout_in_wp_kses_allowed_html' ), 10 );
+
+		if ( AMP_Validation_Utils::should_validate_response() ) {
+			AMP_Validation_Utils::add_validation_hooks();
+		}
 
 		// @todo Add character conversion.
 	}
@@ -204,6 +296,7 @@ public static function purge_amp_query_vars() {
 			'__amp_source_origin',
 			'_wp_amp_action_xhr_converted',
 			'amp_latest_update_time',
+			'amp_last_check_time',
 		);
 
 		// Scrub input vars.
@@ -247,36 +340,217 @@ public static function purge_amp_query_vars() {
 	}
 
 	/**
-	 * Set up commenting.
+	 * Send an HTTP response header.
+	 *
+	 * This largely exists to facilitate unit testing but it also provides a better interface for sending headers.
+	 *
+	 * @since 0.7.0
+	 *
+	 * @param string $name  Header name.
+	 * @param string $value Header value.
+	 * @param array  $args {
+	 *     Args to header().
+	 *
+	 *     @type bool $replace     Whether to replace a header previously sent. Default true.
+	 *     @type int  $status_code Status code to send with the sent header.
+	 * }
+	 * @return bool Whether the header was sent.
 	 */
-	public static function setup_commenting() {
-		if ( ! current_theme_supports( AMP_QUERY_VAR ) ) {
+	public static function send_header( $name, $value, $args = array() ) {
+		$args = array_merge(
+			array(
+				'replace'     => true,
+				'status_code' => null,
+			),
+			$args
+		);
+
+		self::$headers_sent[] = array_merge( compact( 'name', 'value' ), $args );
+		if ( headers_sent() ) {
+			return false;
+		}
+
+		header(
+			sprintf( '%s: %s', $name, $value ),
+			$args['replace'],
+			$args['status_code']
+		);
+		return true;
+	}
+
+	/**
+	 * Hook into a POST form submissions, such as the comment form or some other form submission.
+	 *
+	 * @since 0.7.0
+	 */
+	public static function handle_xhr_request() {
+		$is_amp_xhr = (
+			! empty( self::$purged_amp_query_vars['_wp_amp_action_xhr_converted'] )
+			&&
+			! empty( self::$purged_amp_query_vars['__amp_source_origin'] )
+			&&
+			( ! empty( $_SERVER['REQUEST_METHOD'] ) && 'POST' === $_SERVER['REQUEST_METHOD'] )
+		);
+		if ( ! $is_amp_xhr ) {
 			return;
 		}
 
-		/*
-		 * Temporarily force comments to be listed in descending order.
+		// Send AMP response header.
+		$origin = wp_validate_redirect( wp_sanitize_redirect( esc_url_raw( self::$purged_amp_query_vars['__amp_source_origin'] ) ) );
+		if ( $origin ) {
+			self::send_header( 'AMP-Access-Control-Allow-Source-Origin', $origin, array( 'replace' => true ) );
+		}
+
+		// Intercept POST requests which redirect.
+		add_filter( 'wp_redirect', array( __CLASS__, 'intercept_post_request_redirect' ), PHP_INT_MAX );
+
+		// Add special handling for redirecting after comment submission.
+		add_filter( 'comment_post_redirect', array( __CLASS__, 'filter_comment_post_redirect' ), PHP_INT_MAX, 2 );
+
+		// Add die handler for AMP error display, most likely due to problem with comment.
+		add_filter( 'wp_die_handler', function() {
+			return array( __CLASS__, 'handle_wp_die' );
+		} );
+
+	}
+
+	/**
+	 * Strip tags that are not allowed in amp-mustache.
+	 *
+	 * @since 0.7.0
+	 *
+	 * @param string $text Text to sanitize.
+	 * @return string Sanitized text.
+	 */
+	protected static function wp_kses_amp_mustache( $text ) {
+		$amp_mustache_allowed_html_tags = array( 'strong', 'b', 'em', 'i', 'u', 's', 'small', 'mark', 'del', 'ins', 'sup', 'sub' );
+		return wp_kses( $text, array_fill_keys( $amp_mustache_allowed_html_tags, array() ) );
+	}
+
+	/**
+	 * Handle comment_post_redirect to ensure page reload is done when comments_live_list is not supported, while sending back a success message when it is.
+	 *
+	 * @since 0.7.0
+	 *
+	 * @param string     $url     Comment permalink to redirect to.
+	 * @param WP_Comment $comment Posted comment.
+	 * @return string URL.
+	 */
+	public static function filter_comment_post_redirect( $url, $comment ) {
+		$theme_support = get_theme_support( 'amp' );
+
+		// Cause a page refresh if amp-live-list is not implemented for comments via add_theme_support( 'amp', array( 'comments_live_list' => true ) ).
+		if ( empty( $theme_support[0]['comments_live_list'] ) ) {
+			/*
+			 * Add the comment ID to the URL to force AMP to refresh the page.
+			 * This is ideally a temporary workaround to deal with https://github.com/ampproject/amphtml/issues/14170
+			 */
+			$url = add_query_arg( 'comment', $comment->comment_ID, $url );
+
+			// Pass URL along to wp_redirect().
+			return $url;
+		}
+
+		// Create a success message to display to the user.
+		if ( '1' === (string) $comment->comment_approved ) {
+			$message = __( 'Your comment has been posted.', 'amp' );
+		} else {
+			$message = __( 'Your comment is awaiting moderation.', 'default' ); // Note core string re-use.
+		}
+
+		/**
+		 * Filters the message when comment submitted success message when
 		 *
-		 * The following hooks are temporary while waiting for amphtml#5396 to be resolved.
+		 * @since 0.7
 		 */
-		add_filter( 'option_comment_order', function() {
-			return 'desc';
-		}, PHP_INT_MAX );
-
-		add_action( 'admin_print_footer_scripts-options-discussion.php', function() {
-			?>
-			<div class="notice notice-info inline" id="amp-comment-notice"><p><?php echo wp_kses_post( __( 'Note: AMP does not yet <a href="https://github.com/ampproject/amphtml/issues/5396" target="_blank">support ascending</a> comments with newer entries appearing at the bottom.', 'amp' ) ); ?></p></div>
-			<script>
-			// Move the notice below the selector and disable selector.
-			jQuery( function( $ ) {
-				var orderSelect = $( '#comment_order' ),
-					notice = $( '#amp-comment-notice' );
-				orderSelect.prop( 'disabled', true );
-				orderSelect.closest( 'fieldset' ).append( notice );
-			} );
-			</script>
-			<?php
-		} );
+		$message = apply_filters( 'amp_comment_posted_message', $message, $comment );
+
+		// Message will be shown in template defined by AMP_Theme_Support::amend_comment_form().
+		wp_send_json( array(
+			'message' => self::wp_kses_amp_mustache( $message ),
+		) );
+	}
+
+	/**
+	 * New error handler for AMP form submission.
+	 *
+	 * @since 0.7.0
+	 * @see wp_die()
+	 *
+	 * @param WP_Error|string  $error The error to handle.
+	 * @param string|int       $title Optional. Error title. If `$message` is a `WP_Error` object,
+	 *                                error data with the key 'title' may be used to specify the title.
+	 *                                If `$title` is an integer, then it is treated as the response
+	 *                                code. Default empty.
+	 * @param string|array|int $args {
+	 *     Optional. Arguments to control behavior. If `$args` is an integer, then it is treated
+	 *     as the response code. Default empty array.
+	 *
+	 *     @type int $response The HTTP response code. Default 200 for Ajax requests, 500 otherwise.
+	 * }
+	 */
+	public static function handle_wp_die( $error, $title = '', $args = array() ) {
+		if ( is_int( $title ) ) {
+			$status_code = $title;
+		} elseif ( is_int( $args ) ) {
+			$status_code = $args;
+		} elseif ( is_array( $args ) && isset( $args['response'] ) ) {
+			$status_code = $args['response'];
+		} else {
+			$status_code = 500;
+		}
+		status_header( $status_code );
+
+		if ( is_wp_error( $error ) ) {
+			$error = $error->get_error_message();
+		}
+
+		// Message will be shown in template defined by AMP_Theme_Support::amend_comment_form().
+		wp_send_json( array(
+			'error' => self::wp_kses_amp_mustache( $error ),
+		) );
+	}
+
+	/**
+	 * Intercept the response to a POST request.
+	 *
+	 * @since 0.7.0
+	 * @see wp_redirect()
+	 *
+	 * @param string $location The location to redirect to.
+	 */
+	public static function intercept_post_request_redirect( $location ) {
+
+		// Make sure relative redirects get made absolute.
+		$parsed_location = array_merge(
+			array(
+				'scheme' => 'https',
+				'host'   => wp_parse_url( home_url(), PHP_URL_HOST ),
+				'path'   => isset( $_SERVER['REQUEST_URI'] ) ? strtok( wp_unslash( $_SERVER['REQUEST_URI'] ), '?' ) : '/',
+			),
+			wp_parse_url( $location )
+		);
+
+		$absolute_location = '';
+		if ( 'https' === $parsed_location['scheme'] ) {
+			$absolute_location .= $parsed_location['scheme'] . ':';
+		}
+		$absolute_location .= '//' . $parsed_location['host'];
+		if ( isset( $parsed_location['port'] ) ) {
+			$absolute_location .= ':' . $parsed_location['port'];
+		}
+		$absolute_location .= $parsed_location['path'];
+		if ( isset( $parsed_location['query'] ) ) {
+			$absolute_location .= '?' . $parsed_location['query'];
+		}
+		if ( isset( $parsed_location['fragment'] ) ) {
+			$absolute_location .= '#' . $parsed_location['fragment'];
+		}
+
+		self::send_header( 'AMP-Redirect-To', $absolute_location );
+		self::send_header( 'Access-Control-Expose-Headers', 'AMP-Redirect-To' );
+
+		wp_send_json_success();
 	}
 
 	/**
@@ -349,23 +623,24 @@ public static function register_content_embed_handlers() {
 	 * @param array $args the args for the comments list..
 	 * @return array Args to return.
 	 */
-	public static function amp_set_comments_walker( $args ) {
+	public static function set_comments_walker( $args ) {
 		$amp_walker     = new AMP_Comment_Walker();
 		$args['walker'] = $amp_walker;
-		// Add reverse order here as well, in case theme overrides it.
-		$args['reverse_top_level'] = true;
-
 		return $args;
 	}
 
 	/**
 	 * Adds the form submit success and fail templates.
 	 */
-	public static function add_amp_comment_form_templates() {
+	public static function amend_comment_form() {
 		?>
+		<?php if ( is_singular() && ! amp_is_canonical() ) : ?>
+			<input type="hidden" name="redirect_to" value="<?php echo esc_url( amp_get_permalink( get_the_ID() ) ); ?>">
+		<?php endif; ?>
+
 		<div submit-success>
 			<template type="amp-mustache">
-				<?php esc_html_e( 'Your comment has been posted, but may be subject to moderation.', 'amp' ); ?>
+				<p>{{{message}}}</p>
 			</template>
 		</div>
 		<div submit-error>
@@ -414,16 +689,6 @@ public static function filter_paired_template_include( $template ) {
 		return $template;
 	}
 
-	/**
-	 * Print AMP script and placeholder for others.
-	 *
-	 * @link https://www.ampproject.org/docs/reference/spec#scrpt
-	 */
-	public static function add_amp_component_scripts() {
-		// Replaced after output buffering with all AMP component scripts.
-		echo self::SCRIPTS_PLACEHOLDER; // phpcs:ignore WordPress.Security.EscapeOutput, WordPress.XSS.EscapeOutput
-	}
-
 	/**
 	 * Get canonical URL for current request.
 	 *
@@ -465,13 +730,7 @@ public static function get_current_canonical_url() {
 			$url = add_query_arg( $added_query_vars, $url );
 		}
 
-		// Strip endpoint.
-		$url = preg_replace( ':/' . preg_quote( AMP_QUERY_VAR, ':' ) . '(?=/?(\?|#|$)):', '', $url );
-
-		// Strip query var.
-		$url = remove_query_arg( AMP_QUERY_VAR, $url );
-
-		return $url;
+		return amp_remove_endpoint( $url );
 	}
 
 	/**
@@ -602,62 +861,6 @@ public static function print_amp_styles() {
 		echo "<style amp-custom></style>\n"; // This will by populated by AMP_Style_Sanitizer.
 	}
 
-	/**
-	 * Determine required AMP scripts.
-	 *
-	 * @param array $amp_scripts Initial scripts.
-	 * @return string Scripts to inject into the HEAD.
-	 */
-	public static function get_amp_scripts( $amp_scripts ) {
-
-		foreach ( self::$embed_handlers as $embed_handler ) {
-			$amp_scripts = array_merge(
-				$amp_scripts,
-				$embed_handler->get_scripts()
-			);
-		}
-
-		/**
-		 * List of components that are custom elements.
-		 *
-		 * Per the spec, "Most extensions are custom-elements." In fact, there is only one custom template.
-		 *
-		 * @link https://github.com/ampproject/amphtml/blob/cd685d4e62153557519553ffa2183aedf8c93d62/validator/validator.proto#L326-L328
-		 * @link https://github.com/ampproject/amphtml/blob/cd685d4e62153557519553ffa2183aedf8c93d62/extensions/amp-mustache/validator-amp-mustache.protoascii#L27
-		 */
-		$custom_templates = array( 'amp-mustache' );
-
-		/**
-		 * Filters AMP component scripts before they are injected onto the output buffer for the response.
-		 *
-		 * Plugins may add their own component scripts which have been rendered but which the plugin doesn't yet
-		 * recognize.
-		 *
-		 * @since 0.7
-		 *
-		 * @param array $amp_scripts AMP Component scripts, mapping component names to component source URLs.
-		 */
-		$amp_scripts = apply_filters( 'amp_component_scripts', $amp_scripts );
-
-		$scripts = '<script async src="https://cdn.ampproject.org/v0.js"></script>'; // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
-		foreach ( $amp_scripts as $amp_script_component => $amp_script_source ) {
-
-			$custom_type = 'custom-element';
-			if ( in_array( $amp_script_component, $custom_templates, true ) ) {
-				$custom_type = 'custom-template';
-			}
-
-			$scripts .= sprintf(
-				'<script async %s="%s" src="%s"></script>', // phpcs:ignore WordPress.WP.EnqueuedResources, WordPress.XSS.EscapeOutput.OutputNotEscaped
-				$custom_type,
-				$amp_script_component,
-				$amp_script_source
-			);
-		}
-
-		return $scripts;
-	}
-
 	/**
 	 * Ensure markup required by AMP <https://www.ampproject.org/docs/reference/spec#required-markup>.
 	 *
@@ -666,10 +869,11 @@ public static function get_amp_scripts( $amp_scripts ) {
 	 * canonical URL by default if a singular post.
 	 *
 	 * @since 0.7
+	 * @todo All of this might be better placed inside of a sanitizer.
 	 *
 	 * @param DOMDocument $dom Doc.
 	 */
-	protected static function ensure_required_markup( DOMDocument $dom ) {
+	public static function ensure_required_markup( DOMDocument $dom ) {
 		$head = $dom->getElementsByTagName( 'head' )->item( 0 );
 		if ( ! $head ) {
 			$head = $dom->createElement( 'head' );
@@ -703,7 +907,19 @@ protected static function ensure_required_markup( DOMDocument $dom ) {
 			) );
 			$head->insertBefore( $meta_viewport, $meta_charset->nextSibling );
 		}
-
+		// Prevent schema.org duplicates.
+		$has_schema_org_metadata = false;
+		foreach ( $head->getElementsByTagName( 'script' ) as $script ) {
+			if ( 'application/ld+json' === $script->getAttribute( 'type' ) && false !== strpos( $script->nodeValue, 'schema.org' ) ) {
+				$has_schema_org_metadata = true;
+				break;
+			}
+		}
+		if ( ! $has_schema_org_metadata ) {
+			$script = $dom->createElement( 'script', wp_json_encode( amp_get_schemaorg_metadata() ) );
+			$script->setAttribute( 'type', 'application/ld+json' );
+			$head->appendChild( $script );
+		}
 		// Ensure rel=canonical link.
 		$rel_canonical = null;
 		foreach ( $head->getElementsByTagName( 'link' ) as $link ) {
@@ -721,6 +937,27 @@ protected static function ensure_required_markup( DOMDocument $dom ) {
 		}
 	}
 
+	/**
+	 * Dequeue Customizer assets which are not necessary outside the preview iframe.
+	 *
+	 * Prevent enqueueing customize-preview styles if not in customizer preview iframe.
+	 * These are only needed for when there is live editing of content, such as selective refresh.
+	 *
+	 * @since 0.7
+	 */
+	public static function dequeue_customize_preview_scripts() {
+
+		// Dequeue styles unnecessary unless in customizer preview iframe when editing (such as for edit shortcuts).
+		if ( ! self::is_customize_preview_iframe() ) {
+			wp_dequeue_style( 'customize-preview' );
+			foreach ( wp_styles()->registered as $handle => $dependency ) {
+				if ( in_array( 'customize-preview', $dependency->deps, true ) ) {
+					wp_dequeue_style( $handle );
+				}
+			}
+		}
+	}
+
 	/**
 	 * Start output buffering.
 	 *
@@ -735,11 +972,12 @@ public static function start_output_buffering() {
 		 * Sites with New Relic will need to specially configure New Relic for AMP:
 		 * https://docs.newrelic.com/docs/browser/new-relic-browser/installation/monitor-amp-pages-new-relic-browser
 		 */
-		if ( extension_loaded( 'newrelic' ) ) {
+		if ( function_exists( 'newrelic_disable_autorum' ) ) {
 			newrelic_disable_autorum();
 		}
 
 		ob_start();
+		self::$initial_ob_level = ob_get_level();
 
 		// Note that the following must be at 0 because wp_ob_end_flush_all() runs at shutdown:1.
 		add_action( 'shutdown', array( __CLASS__, 'finish_output_buffering' ), 0 );
@@ -752,9 +990,40 @@ public static function start_output_buffering() {
 	 * @see AMP_Theme_Support::start_output_buffering()
 	 */
 	public static function finish_output_buffering() {
+
+		// Flush output buffer stack until we get to the output buffer we started.
+		while ( ob_get_level() > self::$initial_ob_level ) {
+			ob_end_flush();
+		}
+
 		echo self::prepare_response( ob_get_clean() ); // WPCS: xss ok.
 	}
 
+	/**
+	 * Filter rendered partial to convert to AMP.
+	 *
+	 * @see WP_Customize_Partial::render()
+	 *
+	 * @param string|mixed $partial Rendered partial.
+	 * @return string|mixed Filtered partial.
+	 * @global int $content_width
+	 */
+	public static function filter_customize_partial_render( $partial ) {
+		global $content_width;
+		if ( is_string( $partial ) && preg_match( '/<\w/', $partial ) ) {
+			$dom  = AMP_DOM_Utils::get_dom_from_content( $partial );
+			$args = array(
+				'content_max_width'    => ! empty( $content_width ) ? $content_width : AMP_Post_Template::CONTENT_MAX_WIDTH, // Back-compat.
+				'use_document_element' => false,
+				'allow_dirty_styles'   => true,
+				'allow_dirty_scripts'  => false,
+			);
+			AMP_Content_Sanitizer::sanitize_document( $dom, self::$sanitizer_classes, $args ); // @todo Include script assets in response?
+			$partial = AMP_DOM_Utils::get_content_from_dom( $dom );
+		}
+		return $partial;
+	}
+
 	/**
 	 * Process response to ensure AMP validity.
 	 *
@@ -781,11 +1050,15 @@ public static function prepare_response( $response, $args = array() ) {
 			return $response;
 		}
 
+		$is_validation_debug_mode = ! empty( $_REQUEST[ AMP_Validation_Utils::DEBUG_QUERY_VAR ] ); // WPCS: csrf ok.
+
 		$args = array_merge(
 			array(
 				'content_max_width'       => ! empty( $content_width ) ? $content_width : AMP_Post_Template::CONTENT_MAX_WIDTH, // Back-compat.
 				'use_document_element'    => true,
-				'remove_invalid_callback' => null,
+				'allow_dirty_styles'      => self::is_customize_preview_iframe(), // Dirty styles only needed when editing (e.g. for edit shortcodes).
+				'allow_dirty_scripts'     => is_customize_preview(), // Scripts are always needed to inject changeset UUID.
+				'disable_invalid_removal' => $is_validation_debug_mode,
 			),
 			$args
 		);
@@ -805,7 +1078,18 @@ public static function prepare_response( $response, $args = array() ) {
 		}
 		$dom = AMP_DOM_Utils::get_dom( $response );
 
-		// First ensure the mandatory amp attribute is present on the html element, as otherwise it will be stripped entirely.
+		$xpath = new DOMXPath( $dom );
+
+		$head = $dom->getElementsByTagName( 'head' )->item( 0 );
+
+		if ( isset( $head ) ) {
+			// Make sure scripts from the body get moved to the head.
+			foreach ( $xpath->query( '//body//script[ @custom-element or @custom-template ]' ) as $script ) {
+				$head->appendChild( $script );
+			}
+		}
+
+		// Ensure the mandatory amp attribute is present on the html element, as otherwise it will be stripped entirely.
 		if ( ! $dom->documentElement->hasAttribute( 'amp' ) && ! $dom->documentElement->hasAttribute( '⚡️' ) ) {
 			$dom->documentElement->setAttribute( 'amp', '' );
 		}
@@ -820,17 +1104,82 @@ public static function prepare_response( $response, $args = array() ) {
 			trigger_error( esc_html( sprintf( __( 'The database has the %s encoding when it needs to be utf-8 to work with AMP.', 'amp' ), get_bloginfo( 'charset' ) ) ), E_USER_WARNING ); // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_trigger_error
 		}
 
+		if ( AMP_Validation_Utils::should_validate_response() ) {
+			AMP_Validation_Utils::finalize_validation( $dom, array(
+				'remove_source_comments' => ! $is_validation_debug_mode,
+			) );
+		}
+
 		$response  = "<!DOCTYPE html>\n";
 		$response .= AMP_DOM_Utils::get_content_from_dom_node( $dom, $dom->documentElement );
 
-		// Inject required scripts.
-		$response = preg_replace(
-			'#' . preg_quote( self::SCRIPTS_PLACEHOLDER, '#' ) . '#',
-			self::get_amp_scripts( $assets['scripts'] ),
-			$response,
-			1
-		);
+		$amp_scripts = $assets['scripts'];
+		foreach ( self::$embed_handlers as $embed_handler ) {
+			$amp_scripts = array_merge(
+				$amp_scripts,
+				$embed_handler->get_scripts()
+			);
+		}
+
+		// Allow for embed handlers to override the default extension version by defining a different URL.
+		foreach ( $amp_scripts as $handle => $value ) {
+			if ( is_string( $value ) && wp_script_is( $handle, 'registered' ) ) {
+				wp_scripts()->registered[ $handle ]->src = $value;
+			}
+		}
+
+		/*
+		 * Print additional AMP component scripts which have been discovered by the sanitizers, and inject into the head.
+		 * Before printing the AMP scripts, make sure that no plugins will be manipulating the output to be invalid AMP
+		 * since at this point the sanitizers have completed and won't check what is output here.
+		 */
+		ob_start();
+		$possible_hooks = array( 'wp_print_scripts', 'print_scripts_array', 'script_loader_src', 'clean_url', 'script_loader_tag', 'attribute_escape' );
+		foreach ( $possible_hooks as $possible_hook ) {
+			remove_all_filters( $possible_hook ); // An action and a filter are the same thing.
+		}
+		add_filter( 'script_loader_tag', 'amp_filter_script_loader_tag', PHP_INT_MAX, 2 ); // Make sure this one required filter is present.
+		wp_scripts()->do_items( array_keys( $amp_scripts ) );
+		$script_tags = ob_get_clean();
+		if ( ! empty( $script_tags ) ) {
+			$response = preg_replace(
+				'#(?=</head>)#',
+				$script_tags,
+				$response,
+				1
+			);
+		}
 
 		return $response;
 	}
+
+	/**
+	 * Adds 'data-amp-layout' to the allowed <img> attributes for wp_kses().
+	 *
+	 * @since 0.7
+	 *
+	 * @param array $context Allowed tags and their allowed attributes.
+	 * @return array $context Filtered allowed tags and attributes.
+	 */
+	public static function whitelist_layout_in_wp_kses_allowed_html( $context ) {
+		if ( ! empty( $context['img']['width'] ) && ! empty( $context['img']['height'] ) ) {
+			$context['img']['data-amp-layout'] = true;
+		}
+
+		return $context;
+	}
+
+	/**
+	 * Enqueue AMP assets if this is an AMP endpoint.
+	 *
+	 * @since 0.7
+	 *
+	 * @return void
+	 */
+	public static function enqueue_assets() {
+		wp_enqueue_script( 'amp-runtime' );
+
+		// Enqueue default styles expected by sanitizer.
+		wp_enqueue_style( 'amp-default', amp_get_asset_url( 'css/amp-default.css' ), array(), AMP__VERSION );
+	}
 }
diff --git a/includes/embeds/class-amp-playlist-embed-handler.php b/includes/embeds/class-amp-playlist-embed-handler.php
new file mode 100644
index 00000000000..32eea3d9322
--- /dev/null
+++ b/includes/embeds/class-amp-playlist-embed-handler.php
@@ -0,0 +1,324 @@
+<?php
+/**
+ * Class AMP_Playlist_Embed_Handler
+ *
+ * @package AMP
+ * @since 0.7
+ */
+
+/**
+ * Class AMP_Playlist_Embed_Handler
+ *
+ * Creates AMP-compatible markup for the WordPress 'playlist' shortcode.
+ *
+ * @package AMP
+ */
+class AMP_Playlist_Embed_Handler extends AMP_Base_Embed_Handler {
+
+	/**
+	 * The tag of the shortcode.
+	 *
+	 * @var string
+	 */
+	const SHORTCODE = 'playlist';
+
+	/**
+	 * The default height of the thumbnail image for 'audio' playlist tracks.
+	 *
+	 * @var int
+	 */
+	const DEFAULT_THUMB_HEIGHT = 64;
+
+	/**
+	 * The default width of the thumbnail image for 'audio' playlist tracks.
+	 *
+	 * @var int
+	 */
+	const DEFAULT_THUMB_WIDTH = 48;
+
+	/**
+	 * The max width of the audio thumbnail image.
+	 *
+	 * This corresponds to the max-width in wp-mediaelement.css:
+	 * .wp-playlist .wp-playlist-current-item img
+	 *
+	 * @var int
+	 */
+	const THUMB_MAX_WIDTH = 60;
+
+	/**
+	 * The height of the carousel.
+	 *
+	 * @var int
+	 */
+	const CAROUSEL_HEIGHT = 160;
+
+	/**
+	 * The pattern to get the playlist data.
+	 *
+	 * @var string
+	 */
+	const PLAYLIST_REGEX = ':<script type="application/json" class="wp-playlist-script">(.+?)</script>:s';
+
+	/**
+	 * The ID of individual playlist.
+	 *
+	 * @var int
+	 */
+	public static $playlist_id = 0;
+
+	/**
+	 * The removed shortcode callback.
+	 *
+	 * @var callable
+	 */
+	public $removed_shortcode_callback;
+
+	/**
+	 * Registers the playlist shortcode.
+	 *
+	 * @global array $shortcode_tags
+	 * @return void
+	 */
+	public function register_embed() {
+		global $shortcode_tags;
+		if ( shortcode_exists( self::SHORTCODE ) ) {
+			$this->removed_shortcode_callback = $shortcode_tags[ self::SHORTCODE ];
+		}
+		add_shortcode( self::SHORTCODE, array( $this, 'shortcode' ) );
+		remove_action( 'wp_playlist_scripts', 'wp_playlist_scripts' );
+	}
+
+	/**
+	 * Unregisters the playlist shortcode.
+	 *
+	 * @return void
+	 */
+	public function unregister_embed() {
+		if ( $this->removed_shortcode_callback ) {
+			add_shortcode( self::SHORTCODE, $this->removed_shortcode_callback );
+			$this->removed_shortcode_callback = null;
+		}
+		add_action( 'wp_playlist_scripts', 'wp_playlist_scripts' );
+	}
+
+	/**
+	 * Enqueues the playlist styling.
+	 *
+	 * @return void
+	 */
+	public function enqueue_styles() {
+		wp_enqueue_style(
+			'amp-playlist-shortcode',
+			amp_get_asset_url( 'css/amp-playlist-shortcode.css' ),
+			array( 'wp-mediaelement' ),
+			AMP__VERSION
+		);
+	}
+
+	/**
+	 * Gets AMP-compliant markup for the playlist shortcode.
+	 *
+	 * Uses the JSON that wp_playlist_shortcode() produces.
+	 * Gets the markup, based on the type of playlist.
+	 *
+	 * @param array $attr The playlist attributes.
+	 * @return string Playlist shortcode markup.
+	 */
+	public function shortcode( $attr ) {
+		$data = $this->get_data( $attr );
+		if ( isset( $data['type'] ) && ( 'audio' === $data['type'] ) ) {
+			return $this->audio_playlist( $data );
+		} elseif ( isset( $data['type'] ) && ( 'video' === $data['type'] ) ) {
+			return $this->video_playlist( $data );
+		}
+	}
+
+	/**
+	 * Gets an AMP-compliant audio playlist.
+	 *
+	 * @param array $data Data.
+	 * @return string Playlist shortcode markup, or an empty string.
+	 */
+	public function audio_playlist( $data ) {
+		if ( ! isset( $data['tracks'] ) ) {
+			return '';
+		}
+		self::$playlist_id++;
+		$container_id = 'wpPlaylist' . self::$playlist_id . 'Carousel';
+		$state_id     = 'wpPlaylist' . self::$playlist_id;
+		$amp_state    = array(
+			'selectedIndex' => 0,
+		);
+
+		$this->enqueue_styles();
+		ob_start();
+		?>
+		<div class="wp-playlist wp-audio-playlist wp-playlist-light">
+			<amp-state id="<?php echo esc_attr( $state_id ); ?>">
+				<script type="application/json"><?php echo wp_json_encode( $amp_state ); ?></script>
+			</amp-state>
+			<amp-carousel id="<?php echo esc_attr( $container_id ); ?>" [slide]="<?php echo esc_attr( $state_id . '.selectedIndex' ); ?>" height="<?php echo esc_attr( self::CAROUSEL_HEIGHT ); ?>" width="auto" type="slides">
+				<?php
+				foreach ( $data['tracks'] as $track ) :
+					$title      = $this->get_title( $track );
+					$image_url  = isset( $track['thumb']['src'] ) ? $track['thumb']['src'] : '';
+					$dimensions = $this->get_thumb_dimensions( $track );
+					?>
+					<div>
+						<div class="wp-playlist-current-item">
+							<?php if ( $image_url ) : ?>
+								<amp-img src="<?php echo esc_url( $image_url ); ?>" height="<?php echo esc_attr( $dimensions['height'] ); ?>" width="<?php echo esc_attr( $dimensions['width'] ); ?>"></amp-img>
+							<?php endif; ?>
+							<div class="wp-playlist-caption">
+								<span class="wp-playlist-item-meta wp-playlist-item-title"><?php echo esc_html( $title ); ?></span>
+							</div>
+						</div>
+						<amp-audio width="auto" height="50" src="<?php echo esc_url( $track['src'] ); ?>"></amp-audio>
+					</div>
+				<?php endforeach; ?>
+			</amp-carousel>
+			<?php $this->print_tracks( $state_id, $data['tracks'] ); ?>
+		</div>
+		<?php
+		return ob_get_clean();
+	}
+
+	/**
+	 * Gets an AMP-compliant video playlist.
+	 *
+	 * This uses similar markup to the native playlist shortcode output.
+	 * So the styles from wp-mediaelement.min.css will apply to it.
+	 *
+	 * @global int $content_width
+	 * @param array $data Data.
+	 * @return string $video_playlist Markup for the video playlist.
+	 */
+	public function video_playlist( $data ) {
+		global $content_width;
+		if ( ! isset( $data['tracks'], $data['tracks'][0]['src'] ) ) {
+			return '';
+		}
+		self::$playlist_id++;
+		$state_id  = 'wpPlaylist' . self::$playlist_id;
+		$amp_state = array(
+			'selectedIndex' => 0,
+		);
+		foreach ( $data['tracks'] as $index => $track ) {
+			$amp_state[ $index ] = array(
+				'videoUrl' => $track['src'],
+				'thumb'    => isset( $track['thumb']['src'] ) ? $track['thumb']['src'] : '',
+			);
+		}
+
+		$dimensions = isset( $data['tracks'][0]['dimensions']['resized'] ) ? $data['tracks'][0]['dimensions']['resized'] : null;
+		$width      = isset( $dimensions['width'] ) ? $dimensions['width'] : $content_width;
+		$height     = isset( $dimensions['height'] ) ? $dimensions['height'] : null;
+		$src_bound  = sprintf( '%s[%s.selectedIndex].videoUrl', $state_id, $state_id );
+
+		$this->enqueue_styles();
+		ob_start();
+		?>
+		<div class="wp-playlist wp-video-playlist wp-playlist-light">
+			<amp-state id="<?php echo esc_attr( $state_id ); ?>">
+				<script type="application/json"><?php echo wp_json_encode( $amp_state ); // WPCS: XSS ok. ?></script>
+			</amp-state>
+			<amp-video id="amp-video" src="<?php echo esc_url( $data['tracks'][0]['src'] ); ?>" [src]="<?php echo esc_attr( $src_bound ); ?>" width="<?php echo esc_attr( $width ); ?>" height="<?php echo esc_attr( $height ); ?>" controls></amp-video>
+			<?php $this->print_tracks( $state_id, $data['tracks'] ); ?>
+		</div>
+		<?php
+		return ob_get_clean(); // WPCS: XSS ok.
+	}
+
+	/**
+	 * Gets the thumbnail image dimensions, including height and width.
+	 *
+	 * If the width is higher than the maximum width,
+	 * reduces it to the maximum width.
+	 * And it proportionally reduces the height.
+	 *
+	 * @param array $track The data for the track.
+	 * @return array {
+	 *     Dimensions.
+	 *
+	 *     @type int $height Image height.
+	 *     @type int $width  Image width.
+	 * }
+	 */
+	public function get_thumb_dimensions( $track ) {
+		$original_height = isset( $track['thumb']['height'] ) ? intval( $track['thumb']['height'] ) : self::DEFAULT_THUMB_HEIGHT;
+		$original_width  = isset( $track['thumb']['width'] ) ? intval( $track['thumb']['width'] ) : self::DEFAULT_THUMB_WIDTH;
+		if ( $original_width > self::THUMB_MAX_WIDTH ) {
+			$ratio  = $original_width / self::THUMB_MAX_WIDTH;
+			$height = intval( $original_height / $ratio );
+		} else {
+			$height = $original_height;
+		}
+		$width = min( self::THUMB_MAX_WIDTH, $original_width );
+		return compact( 'height', 'width' );
+	}
+
+	/**
+	 * Outputs the playlist tracks, based on the type of playlist.
+	 *
+	 * These typically appear below the player.
+	 * Clicking a track triggers the player to appear with its src.
+	 *
+	 * @param string $state_id The ID of the container.
+	 * @param array  $tracks   Tracks.
+	 * @return void
+	 */
+	public function print_tracks( $state_id, $tracks ) {
+		?>
+		<div class="wp-playlist-tracks">
+			<?php foreach ( $tracks as $index => $track ) : ?>
+				<?php
+				$on            = 'tap:AMP.setState(' . wp_json_encode( array( $state_id => array( 'selectedIndex' => $index ) ) ) . ')';
+				$initial_class = 0 === $index ? 'wp-playlist-item wp-playlist-playing' : 'wp-playlist-item';
+				$bound_class   = sprintf( '%d == %s.selectedIndex ? "wp-playlist-item wp-playlist-playing" : "wp-playlist-item"', $index, $state_id );
+				?>
+				<div class="<?php echo esc_attr( $initial_class ); ?>" [class]="<?php echo esc_attr( $bound_class ); ?>" >
+					<a class="wp-playlist-caption" on="<?php echo esc_attr( $on ); ?>">
+						<?php echo esc_html( strval( $index + 1 ) . '.' ); ?> <span class="wp-playlist-item-title"><?php echo esc_html( $this->get_title( $track ) ); ?></span>
+					</a>
+					<?php if ( isset( $track['meta']['length_formatted'] ) ) : ?>
+						<div class="wp-playlist-item-length"><?php echo esc_html( $track['meta']['length_formatted'] ); ?></div>
+					<?php endif; ?>
+				</div>
+			<?php endforeach; ?>
+		</div>
+		<?php
+	}
+
+	/**
+	 * Gets the data for the playlist.
+	 *
+	 * @see wp_playlist_shortcode()
+	 * @param array $attr The shortcode attributes.
+	 * @return array $data The data for the playlist.
+	 */
+	public function get_data( $attr ) {
+		$markup = wp_playlist_shortcode( $attr );
+		preg_match( self::PLAYLIST_REGEX, $markup, $matches );
+		if ( empty( $matches[1] ) ) {
+			return array();
+		}
+		return json_decode( $matches[1], true );
+	}
+
+	/**
+	 * Gets the title for the track.
+	 *
+	 * @param array $track The track data.
+	 * @return string $title The title of the track.
+	 */
+	public function get_title( $track ) {
+		if ( ! empty( $track['caption'] ) ) {
+			return $track['caption'];
+		} elseif ( ! empty( $track['title'] ) ) {
+			return $track['title'];
+		}
+		return '';
+	}
+
+}
diff --git a/includes/options/class-amp-options-manager.php b/includes/options/class-amp-options-manager.php
index 72109f104a1..84de7c26b43 100644
--- a/includes/options/class-amp-options-manager.php
+++ b/includes/options/class-amp-options-manager.php
@@ -172,7 +172,7 @@ public static function check_supported_post_type_update_errors() {
 				continue;
 			}
 
-			$post_type_supported = post_type_supports( $post_type->name, AMP_QUERY_VAR );
+			$post_type_supported = post_type_supports( $post_type->name, amp_get_slug() );
 			$is_support_elected  = in_array( $post_type->name, $supported_types, true );
 
 			$error = null;
diff --git a/includes/options/class-amp-options-menu.php b/includes/options/class-amp-options-menu.php
index a06d5f4169a..3bc556a551f 100644
--- a/includes/options/class-amp-options-menu.php
+++ b/includes/options/class-amp-options-menu.php
@@ -22,7 +22,7 @@ class AMP_Options_Menu {
 	 */
 	public function init() {
 		add_action( 'admin_post_amp_analytics_options', 'AMP_Options_Manager::handle_analytics_submit' );
-		add_action( 'admin_menu', array( $this, 'add_menu_items' ) );
+		add_action( 'admin_menu', array( $this, 'add_menu_items' ), 9 );
 	}
 
 	/**
@@ -94,7 +94,7 @@ public function render_post_types_support() {
 					id="<?php echo esc_attr( $element_id ); ?>"
 					name="<?php echo esc_attr( $element_name ); ?>"
 					value="<?php echo esc_attr( $post_type->name ); ?>"
-					<?php checked( true, amp_is_canonical() || post_type_supports( $post_type->name, AMP_QUERY_VAR ) ); ?>
+					<?php checked( true, amp_is_canonical() || post_type_supports( $post_type->name, amp_get_slug() ) ); ?>
 					<?php disabled( $is_builtin ); ?>
 					>
 				<label for="<?php echo esc_attr( $element_id ); ?>">
diff --git a/includes/sanitizers/class-amp-allowed-tags-generated.php b/includes/sanitizers/class-amp-allowed-tags-generated.php
index 1d13a277ec6..d7e28aecf92 100644
--- a/includes/sanitizers/class-amp-allowed-tags-generated.php
+++ b/includes/sanitizers/class-amp-allowed-tags-generated.php
@@ -13,8 +13,8 @@
  */
 class AMP_Allowed_Tags_Generated {
 
-	private static $spec_file_revision = 527;
-	private static $minimum_validator_revision_required = 265;
+	private static $spec_file_revision = 595;
+	private static $minimum_validator_revision_required = 322;
 
 	private static $allowed_tags = array(
 		'a' => array(
@@ -30,9 +30,11 @@ class AMP_Allowed_Tags_Generated {
 							'allow_relative' => true,
 							'allowed_protocol' => array(
 								'ftp',
+								'geo',
 								'http',
 								'https',
 								'mailto',
+								'maps',
 								'bbmi',
 								'fb-messenger',
 								'intent',
@@ -52,6 +54,7 @@ class AMP_Allowed_Tags_Generated {
 					'hreflang' => array(),
 					'media' => array(),
 					'name' => array(),
+					'referrerpolicy' => array(),
 					'rel' => array(
 						'blacklisted_value_regex' => '(^|\\s)(components|dns-prefetch|import|manifest|preconnect|prefetch|preload|prerender|serviceworker|stylesheet|subresource|)(\\s|$)',
 					),
@@ -114,6 +117,9 @@ class AMP_Allowed_Tags_Generated {
 					'disable-session-states' => array(
 						'value' => '',
 					),
+					'expand-single-section' => array(
+						'value' => '',
+					),
 				),
 				'tag_spec' => array(
 					'requires_extension' => array(
@@ -132,6 +138,7 @@ class AMP_Allowed_Tags_Generated {
 					'noloading' => array(
 						'value' => '',
 					),
+					'rtc-config' => array(),
 					'src' => array(
 						'blacklisted_value_regex' => '__amp_source_origin',
 						'value_url' => array(
@@ -141,6 +148,7 @@ class AMP_Allowed_Tags_Generated {
 							),
 						),
 					),
+					'template' => array(),
 					'type' => array(
 						'mandatory' => true,
 					),
@@ -171,6 +179,7 @@ class AMP_Allowed_Tags_Generated {
 					'noloading' => array(
 						'value' => '',
 					),
+					'rtc-config' => array(),
 					'src' => array(
 						'blacklisted_value_regex' => '__amp_source_origin',
 						'value_url' => array(
@@ -202,6 +211,48 @@ class AMP_Allowed_Tags_Generated {
 					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-ad',
 				),
 			),
+			array(
+				'attr_spec_list' => array(
+					'alt' => array(),
+					'data-enable-refresh' => array(
+						'dispatch_key' => 2,
+						'mandatory' => true,
+						'value' => '',
+					),
+					'json' => array(),
+					'media' => array(),
+					'noloading' => array(
+						'value' => '',
+					),
+					'src' => array(
+						'blacklisted_value_regex' => '__amp_source_origin',
+						'value_url' => array(
+							'allow_relative' => true,
+							'allowed_protocol' => array(
+								'https',
+							),
+						),
+					),
+					'type' => array(
+						'mandatory' => true,
+					),
+				),
+				'tag_spec' => array(
+					'also_requires_tag_warning' => array(
+						'amp-ad extension .js script',
+					),
+					'disallowed_ancestor' => array(
+						'amp-app-banner',
+						'amp-fx-flying-carpet',
+						'amp-lightbox',
+					),
+					'requires_extension' => array(
+						'amp-ad',
+					),
+					'spec_name' => 'amp-ad with data-enable-refresh attribute',
+					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-ad',
+				),
+			),
 		),
 		'amp-analytics' => array(
 			array(
@@ -342,6 +393,9 @@ class AMP_Allowed_Tags_Generated {
 					'noloading' => array(
 						'value' => '',
 					),
+					'preload' => array(
+						'value_regex_casei' => '(auto|metadata|none|)',
+					),
 					'src' => array(
 						'blacklisted_value_regex' => '__amp_source_origin',
 						'value_url' => array(
@@ -423,6 +477,78 @@ class AMP_Allowed_Tags_Generated {
 				),
 			),
 		),
+		'amp-beopinion' => array(
+			array(
+				'attr_spec_list' => array(
+					'data-account' => array(
+						'mandatory' => true,
+						'value_regex_casei' => '[0-9a-f]{24}',
+					),
+					'data-content' => array(
+						'value_regex_casei' => '[0-9a-f]{24}',
+					),
+					'data-my-content' => array(
+						'value_regex' => '0|1',
+					),
+					'data-name' => array(),
+					'media' => array(),
+					'noloading' => array(
+						'value' => '',
+					),
+				),
+				'tag_spec' => array(
+					'requires_extension' => array(
+						'amp-beopinion',
+					),
+				),
+			),
+		),
+		'amp-bind-macro' => array(
+			array(
+				'attr_spec_list' => array(
+					'arguments' => array(),
+					'expression' => array(
+						'mandatory' => true,
+					),
+					'id' => array(
+						'mandatory' => true,
+					),
+				),
+				'tag_spec' => array(
+					'requires_extension' => array(
+						'amp-bind',
+					),
+					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-bind',
+				),
+			),
+		),
+		'amp-bodymovin-animation' => array(
+			array(
+				'attr_spec_list' => array(
+					'loop' => array(
+						'value_regex_casei' => '(false|number|true)',
+					),
+					'noautoplay' => array(
+						'value' => '',
+					),
+					'src' => array(
+						'mandatory' => true,
+						'value_url' => array(
+							'allow_relative' => false,
+							'allowed_protocol' => array(
+								'https',
+							),
+						),
+					),
+				),
+				'tag_spec' => array(
+					'requires_extension' => array(
+						'amp-bodymovin-animation',
+					),
+					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-bodymovin-animation',
+				),
+			),
+		),
 		'amp-brid-player' => array(
 			array(
 				'attr_spec_list' => array(
@@ -482,6 +608,27 @@ class AMP_Allowed_Tags_Generated {
 				),
 			),
 		),
+		'amp-byside-content' => array(
+			array(
+				'attr_spec_list' => array(
+					'data-label' => array(
+						'mandatory' => true,
+					),
+					'data-webcare-id' => array(
+						'mandatory' => true,
+					),
+					'media' => array(),
+					'noloading' => array(
+						'value' => '',
+					),
+				),
+				'tag_spec' => array(
+					'requires_extension' => array(
+						'amp-byside-content',
+					),
+				),
+			),
+		),
 		'amp-call-tracking' => array(
 			array(
 				'attr_spec_list' => array(
@@ -525,6 +672,13 @@ class AMP_Allowed_Tags_Generated {
 					'dots' => array(
 						'value' => '',
 					),
+					'lightbox' => array(),
+					'lightbox-exclude' => array(
+						'value' => '',
+					),
+					'lightbox-thumbnail-id' => array(
+						'value_regex_casei' => '^[a-z][a-z\\d_-]*',
+					),
 					'loop' => array(
 						'value' => '',
 					),
@@ -544,6 +698,22 @@ class AMP_Allowed_Tags_Generated {
 				),
 			),
 		),
+		'amp-consent' => array(
+			array(
+				'attr_spec_list' => array(
+					'media' => array(),
+					'noloading' => array(
+						'value' => '',
+					),
+				),
+				'tag_spec' => array(
+					'requires_extension' => array(
+						'amp-consent',
+					),
+					'unique' => true,
+				),
+			),
+		),
 		'amp-dailymotion' => array(
 			array(
 				'attr_spec_list' => array(
@@ -586,15 +756,45 @@ class AMP_Allowed_Tags_Generated {
 				),
 			),
 		),
-		'amp-embed' => array(
+		'amp-date-picker' => array(
 			array(
 				'attr_spec_list' => array(
-					'alt' => array(),
-					'json' => array(),
+					'allow-blocked-ranges' => array(
+						'value' => '',
+					),
+					'blocked' => array(),
+					'day-size' => array(
+						'value_regex' => '[0-9]+',
+					),
+					'first-day-of-week' => array(
+						'value_regex' => '[0-6]',
+					),
+					'format' => array(),
+					'fullscreen' => array(
+						'value' => '',
+					),
+					'highlighted' => array(),
+					'input-selector' => array(),
+					'locale' => array(),
+					'max' => array(),
 					'media' => array(),
+					'min' => array(),
+					'mode' => array(
+						'value_casei' => 'static',
+					),
+					'month-format' => array(),
 					'noloading' => array(
 						'value' => '',
 					),
+					'number-of-months' => array(
+						'value_regex' => '[0-9]+',
+					),
+					'open-after-clear' => array(
+						'value' => '',
+					),
+					'open-after-select' => array(
+						'value' => '',
+					),
 					'src' => array(
 						'blacklisted_value_regex' => '__amp_source_origin',
 						'value_url' => array(
@@ -605,35 +805,53 @@ class AMP_Allowed_Tags_Generated {
 						),
 					),
 					'type' => array(
-						'mandatory' => true,
+						'value_casei' => 'single',
 					),
+					'week-day-format' => array(),
 				),
 				'tag_spec' => array(
-					'also_requires_tag_warning' => array(
-						'amp-ad extension .js script',
-					),
-					'disallowed_ancestor' => array(
-						'amp-app-banner',
-					),
 					'requires_extension' => array(
-						'amp-ad',
+						'amp-date-picker',
 					),
-					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-ad',
+					'spec_name' => 'amp-date-picker[type=single][mode=static]',
 				),
 			),
 			array(
 				'attr_spec_list' => array(
-					'alt' => array(),
-					'data-multi-size' => array(
-						'dispatch_key' => 2,
-						'mandatory' => true,
+					'allow-blocked-ranges' => array(
 						'value' => '',
 					),
-					'json' => array(),
+					'blocked' => array(),
+					'day-size' => array(
+						'value_regex' => '[0-9]+',
+					),
+					'first-day-of-week' => array(
+						'value_regex' => '[0-6]',
+					),
+					'format' => array(),
+					'highlighted' => array(),
+					'input-selector' => array(),
+					'locale' => array(),
+					'max' => array(),
 					'media' => array(),
+					'min' => array(),
+					'mode' => array(
+						'mandatory' => true,
+						'value_casei' => 'overlay',
+					),
+					'month-format' => array(),
 					'noloading' => array(
 						'value' => '',
 					),
+					'number-of-months' => array(
+						'value_regex' => '[0-9]+',
+					),
+					'open-after-clear' => array(
+						'value' => '',
+					),
+					'open-after-select' => array(
+						'value' => '',
+					),
 					'src' => array(
 						'blacklisted_value_regex' => '__amp_source_origin',
 						'value_url' => array(
@@ -644,69 +862,274 @@ class AMP_Allowed_Tags_Generated {
 						),
 					),
 					'type' => array(
-						'mandatory' => true,
-					),
-				),
-				'tag_spec' => array(
-					'also_requires_tag_warning' => array(
-						'amp-ad extension .js script',
-					),
-					'disallowed_ancestor' => array(
-						'amp-app-banner',
-						'amp-carousel',
-						'amp-fx-flying-carpet',
-						'amp-lightbox',
-						'amp-sticky-ad',
-					),
-					'requires_extension' => array(
-						'amp-ad',
+						'value_casei' => 'single',
 					),
-					'spec_name' => 'amp-embed with data-multi-size attribute',
-					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-ad',
+					'week-day-format' => array(),
 				),
-			),
-		),
-		'amp-experiment' => array(
-			array(
-				'attr_spec_list' => array(),
 				'tag_spec' => array(
 					'requires_extension' => array(
-						'amp-experiment',
+						'amp-date-picker',
 					),
-					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-experiment',
-					'unique' => true,
+					'spec_name' => 'amp-date-picker[type=single][mode=overlay]',
 				),
 			),
-		),
-		'amp-facebook' => array(
 			array(
 				'attr_spec_list' => array(
-					'data-href' => array(
-						'mandatory' => true,
+					'allow-blocked-ranges' => array(
+						'value' => '',
+					),
+					'blocked' => array(),
+					'day-size' => array(
+						'value_regex' => '[0-9]+',
+					),
+					'end-input-selector' => array(),
+					'first-day-of-week' => array(
+						'value_regex' => '[0-6]',
+					),
+					'format' => array(),
+					'fullscreen' => array(
+						'value' => '',
 					),
+					'highlighted' => array(),
+					'locale' => array(),
+					'max' => array(),
 					'media' => array(),
+					'min' => array(),
+					'mode' => array(
+						'value_casei' => 'static',
+					),
+					'month-format' => array(),
 					'noloading' => array(
 						'value' => '',
 					),
+					'number-of-months' => array(
+						'value_regex' => '[0-9]+',
+					),
+					'open-after-clear' => array(
+						'value' => '',
+					),
+					'open-after-select' => array(
+						'value' => '',
+					),
+					'src' => array(
+						'blacklisted_value_regex' => '__amp_source_origin',
+						'value_url' => array(
+							'allow_relative' => true,
+							'allowed_protocol' => array(
+								'https',
+							),
+						),
+					),
+					'start-input-selector' => array(),
+					'type' => array(
+						'mandatory' => true,
+						'value_casei' => 'range',
+					),
+					'week-day-format' => array(),
 				),
 				'tag_spec' => array(
 					'requires_extension' => array(
-						'amp-facebook',
+						'amp-date-picker',
 					),
+					'spec_name' => 'amp-date-picker[type=range][mode=static]',
 				),
 			),
-		),
-		'amp-facebook-comments' => array(
 			array(
 				'attr_spec_list' => array(
-					'data-href' => array(
-						'mandatory' => true,
-					),
-					'media' => array(),
-					'noloading' => array(
+					'allow-blocked-ranges' => array(
 						'value' => '',
 					),
-				),
+					'blocked' => array(),
+					'day-size' => array(
+						'value_regex' => '[0-9]+',
+					),
+					'end-input-selector' => array(),
+					'first-day-of-week' => array(
+						'value_regex' => '[0-6]',
+					),
+					'format' => array(),
+					'highlighted' => array(),
+					'locale' => array(),
+					'max' => array(),
+					'media' => array(),
+					'min' => array(),
+					'mode' => array(
+						'mandatory' => true,
+						'value_casei' => 'overlay',
+					),
+					'month-format' => array(),
+					'noloading' => array(
+						'value' => '',
+					),
+					'number-of-months' => array(
+						'value_regex' => '[0-9]+',
+					),
+					'open-after-clear' => array(
+						'value' => '',
+					),
+					'open-after-select' => array(
+						'value' => '',
+					),
+					'src' => array(
+						'blacklisted_value_regex' => '__amp_source_origin',
+						'value_url' => array(
+							'allow_relative' => true,
+							'allowed_protocol' => array(
+								'https',
+							),
+						),
+					),
+					'start-input-selector' => array(),
+					'type' => array(
+						'mandatory' => true,
+						'value_casei' => 'range',
+					),
+					'week-day-format' => array(),
+				),
+				'tag_spec' => array(
+					'requires_extension' => array(
+						'amp-date-picker',
+					),
+					'spec_name' => 'amp-date-picker[type=range][mode=overlay]',
+				),
+			),
+		),
+		'amp-document-recommendations' => array(
+			array(
+				'attr_spec_list' => array(),
+				'tag_spec' => array(
+					'mandatory_parent' => 'body',
+					'requires_extension' => array(
+						'amp-document-recommendations',
+					),
+					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-document-recommendations',
+				),
+			),
+		),
+		'amp-embed' => array(
+			array(
+				'attr_spec_list' => array(
+					'alt' => array(),
+					'json' => array(),
+					'media' => array(),
+					'noloading' => array(
+						'value' => '',
+					),
+					'rtc-config' => array(),
+					'src' => array(
+						'blacklisted_value_regex' => '__amp_source_origin',
+						'value_url' => array(
+							'allow_relative' => true,
+							'allowed_protocol' => array(
+								'https',
+							),
+						),
+					),
+					'template' => array(),
+					'type' => array(
+						'mandatory' => true,
+					),
+				),
+				'tag_spec' => array(
+					'also_requires_tag_warning' => array(
+						'amp-ad extension .js script',
+					),
+					'disallowed_ancestor' => array(
+						'amp-app-banner',
+					),
+					'requires_extension' => array(
+						'amp-ad',
+					),
+					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-ad',
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'alt' => array(),
+					'data-multi-size' => array(
+						'dispatch_key' => 2,
+						'mandatory' => true,
+						'value' => '',
+					),
+					'json' => array(),
+					'media' => array(),
+					'noloading' => array(
+						'value' => '',
+					),
+					'rtc-config' => array(),
+					'src' => array(
+						'blacklisted_value_regex' => '__amp_source_origin',
+						'value_url' => array(
+							'allow_relative' => true,
+							'allowed_protocol' => array(
+								'https',
+							),
+						),
+					),
+					'type' => array(
+						'mandatory' => true,
+					),
+				),
+				'tag_spec' => array(
+					'also_requires_tag_warning' => array(
+						'amp-ad extension .js script',
+					),
+					'disallowed_ancestor' => array(
+						'amp-app-banner',
+						'amp-carousel',
+						'amp-fx-flying-carpet',
+						'amp-lightbox',
+						'amp-sticky-ad',
+					),
+					'requires_extension' => array(
+						'amp-ad',
+					),
+					'spec_name' => 'amp-embed with data-multi-size attribute',
+					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-ad',
+				),
+			),
+		),
+		'amp-experiment' => array(
+			array(
+				'attr_spec_list' => array(),
+				'tag_spec' => array(
+					'requires_extension' => array(
+						'amp-experiment',
+					),
+					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-experiment',
+					'unique' => true,
+				),
+			),
+		),
+		'amp-facebook' => array(
+			array(
+				'attr_spec_list' => array(
+					'data-href' => array(
+						'mandatory' => true,
+					),
+					'media' => array(),
+					'noloading' => array(
+						'value' => '',
+					),
+				),
+				'tag_spec' => array(
+					'requires_extension' => array(
+						'amp-facebook',
+					),
+				),
+			),
+		),
+		'amp-facebook-comments' => array(
+			array(
+				'attr_spec_list' => array(
+					'data-href' => array(
+						'mandatory' => true,
+					),
+					'media' => array(),
+					'noloading' => array(
+						'value' => '',
+					),
+				),
 				'tag_spec' => array(
 					'requires_extension' => array(
 						'amp-facebook-comments',
@@ -739,6 +1162,31 @@ class AMP_Allowed_Tags_Generated {
 				),
 			),
 		),
+		'amp-facebook-page' => array(
+			array(
+				'attr_spec_list' => array(
+					'data-href' => array(
+						'mandatory' => true,
+						'value_url' => array(
+							'allow_relative' => false,
+							'allowed_protocol' => array(
+								'http',
+								'https',
+							),
+						),
+					),
+					'media' => array(),
+					'noloading' => array(
+						'value' => '',
+					),
+				),
+				'tag_spec' => array(
+					'requires_extension' => array(
+						'amp-facebook-page',
+					),
+				),
+			),
+		),
 		'amp-fit-text' => array(
 			array(
 				'attr_spec_list' => array(
@@ -866,9 +1314,7 @@ class AMP_Allowed_Tags_Generated {
 			array(
 				'attr_spec_list' => array(
 					'[src]' => array(),
-					'allow' => array(
-						'value_regex' => 'geolocation|fullscreen|payment|transparency',
-					),
+					'allow' => array(),
 					'allowfullscreen' => array(
 						'value' => '',
 					),
@@ -915,6 +1361,9 @@ class AMP_Allowed_Tags_Generated {
 		'amp-ima-video' => array(
 			array(
 				'attr_spec_list' => array(
+					'autoplay' => array(
+						'value' => '',
+					),
 					'data-src' => array(
 						'blacklisted_value_regex' => '__amp_source_origin',
 						'value_url' => array(
@@ -971,6 +1420,13 @@ class AMP_Allowed_Tags_Generated {
 					'[srcset]' => array(),
 					'alt' => array(),
 					'attribution' => array(),
+					'lightbox' => array(),
+					'lightbox-exclude' => array(
+						'value' => '',
+					),
+					'lightbox-thumbnail-id' => array(
+						'value_regex_casei' => '^[a-z][a-z\\d_-]*',
+					),
 					'media' => array(),
 					'noloading' => array(
 						'value' => '',
@@ -1165,6 +1621,9 @@ class AMP_Allowed_Tags_Generated {
 					'noloading' => array(
 						'value' => '',
 					),
+					'reset-on-refresh' => array(
+						'value' => '',
+					),
 					'single-item' => array(),
 					'src' => array(
 						'blacklisted_value_regex' => '__amp_source_origin',
@@ -1184,6 +1643,37 @@ class AMP_Allowed_Tags_Generated {
 					),
 				),
 			),
+			array(
+				'attr_spec_list' => array(
+					'[src]' => array(
+						'mandatory' => true,
+					),
+					'credentials' => array(),
+					'items' => array(),
+					'max-items' => array(),
+					'media' => array(),
+					'noloading' => array(
+						'value' => '',
+					),
+					'single-item' => array(),
+					'src' => array(
+						'blacklisted_value_regex' => '__amp_source_origin',
+						'value_url' => array(
+							'allow_relative' => true,
+							'allowed_protocol' => array(
+								'https',
+							),
+						),
+					),
+					'template' => array(),
+				),
+				'tag_spec' => array(
+					'requires_extension' => array(
+						'amp-list',
+					),
+					'spec_name' => 'AMP-LIST [SRC]',
+				),
+			),
 		),
 		'amp-live-list' => array(
 			array(
@@ -1201,6 +1691,9 @@ class AMP_Allowed_Tags_Generated {
 					'id' => array(
 						'mandatory' => true,
 					),
+					'sort' => array(
+						'value_regex' => 'ascending',
+					),
 				),
 				'tag_spec' => array(
 					'requires_extension' => array(
@@ -1209,6 +1702,25 @@ class AMP_Allowed_Tags_Generated {
 				),
 			),
 		),
+		'amp-mathml' => array(
+			array(
+				'attr_spec_list' => array(
+					'data-formula' => array(
+						'mandatory' => true,
+					),
+					'inline' => array(),
+					'media' => array(),
+					'noloading' => array(
+						'value' => '',
+					),
+				),
+				'tag_spec' => array(
+					'requires_extension' => array(
+						'amp-mathml',
+					),
+				),
+			),
+		),
 		'amp-nexxtv-player' => array(
 			array(
 				'attr_spec_list' => array(
@@ -1231,7 +1743,6 @@ class AMP_Allowed_Tags_Generated {
 							),
 						),
 					),
-					'data-seek-to' => array(),
 					'data-streamtype' => array(
 						'value_regex' => 'album|audio|live|playlist|playlist-marked|video',
 					),
@@ -1295,6 +1806,7 @@ class AMP_Allowed_Tags_Generated {
 		'amp-pinterest' => array(
 			array(
 				'attr_spec_list' => array(
+					'alt' => array(),
 					'data-do' => array(
 						'mandatory' => true,
 					),
@@ -1314,6 +1826,7 @@ class AMP_Allowed_Tags_Generated {
 		'amp-pixel' => array(
 			array(
 				'attr_spec_list' => array(
+					'allow-ssr-img' => array(),
 					'media' => array(),
 					'noloading' => array(
 						'value' => '',
@@ -1433,14 +1946,35 @@ class AMP_Allowed_Tags_Generated {
 				),
 			),
 		),
-		'amp-selector' => array(
+		'amp-riddle-quiz' => array(
 			array(
 				'attr_spec_list' => array(
-					'[selected]' => array(),
-					'disabled' => array(
+					'data-riddle-id' => array(
+						'mandatory' => true,
+						'value_regex' => '[0-9]+',
+					),
+					'media' => array(),
+					'noloading' => array(
 						'value' => '',
 					),
-					'form' => array(),
+				),
+				'tag_spec' => array(
+					'requires_extension' => array(
+						'amp-riddle-quiz',
+					),
+					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-riddle-quiz',
+				),
+			),
+		),
+		'amp-selector' => array(
+			array(
+				'attr_spec_list' => array(
+					'[disabled]' => array(),
+					'[selected]' => array(),
+					'disabled' => array(
+						'value' => '',
+					),
+					'form' => array(),
 					'keyboard-select-mode' => array(
 						'value_regex_casei' => 'focus|none|select',
 					),
@@ -1600,6 +2134,7 @@ class AMP_Allowed_Tags_Generated {
 					'id' => array(
 						'mandatory' => true,
 					),
+					'overridable' => array(),
 					'src' => array(
 						'blacklisted_value_regex' => '__amp_source_origin',
 						'value_url' => array(
@@ -1670,6 +2205,27 @@ class AMP_Allowed_Tags_Generated {
 				),
 			),
 		),
+		'amp-story-auto-ads' => array(
+			array(
+				'attr_spec_list' => array(),
+				'tag_spec' => array(
+					'mandatory_parent' => 'amp-story',
+					'requires_extension' => array(
+						'amp-story-auto-ads',
+					),
+					'spec_url' => 'https://github.com/ampproject/amphtml/blob/master/extensions/amp-story/amp-story-auto-ads.md',
+					'unique' => true,
+				),
+			),
+		),
+		'amp-story-cta-layer' => array(
+			array(
+				'attr_spec_list' => array(),
+				'tag_spec' => array(
+					'mandatory_ancestor' => 'amp-story-page',
+				),
+			),
+		),
 		'amp-story-grid-layer' => array(
 			array(
 				'attr_spec_list' => array(
@@ -1816,6 +2372,13 @@ class AMP_Allowed_Tags_Generated {
 					'disableremoteplayback' => array(
 						'value' => '',
 					),
+					'lightbox' => array(),
+					'lightbox-exclude' => array(
+						'value' => '',
+					),
+					'lightbox-thumbnail-id' => array(
+						'value_regex_casei' => '^[a-z][a-z\\d_-]*',
+					),
 					'loop' => array(
 						'value' => '',
 					),
@@ -2040,6 +2603,25 @@ class AMP_Allowed_Tags_Generated {
 				),
 			),
 		),
+		'amp-wistia-player' => array(
+			array(
+				'attr_spec_list' => array(
+					'data-media-hashed-id' => array(
+						'mandatory' => true,
+						'value_regex' => '[0-9a-zA-Z]+',
+					),
+					'media' => array(),
+					'noloading' => array(
+						'value' => '',
+					),
+				),
+				'tag_spec' => array(
+					'requires_extension' => array(
+						'amp-wistia-player',
+					),
+				),
+			),
+		),
 		'amp-youtube' => array(
 			array(
 				'attr_spec_list' => array(
@@ -2048,10 +2630,19 @@ class AMP_Allowed_Tags_Generated {
 					'credentials' => array(
 						'value_regex_casei' => '(include|omit)',
 					),
+					'data-live-channelid' => array(
+						'value_regex' => '[^=/?:]+',
+					),
 					'data-videoid' => array(
-						'mandatory' => true,
 						'value_regex' => '[^=/?:]+',
 					),
+					'lightbox' => array(),
+					'lightbox-exclude' => array(
+						'value' => '',
+					),
+					'lightbox-thumbnail-id' => array(
+						'value_regex_casei' => '^[a-z][a-z\\d_-]*',
+					),
 					'media' => array(),
 					'noloading' => array(
 						'value' => '',
@@ -2601,7 +3192,6 @@ class AMP_Allowed_Tags_Generated {
 				'attr_spec_list' => array(
 					'align' => array(),
 					'submit-success' => array(
-						'dispatch_key' => 1,
 						'mandatory' => true,
 					),
 				),
@@ -2610,11 +3200,25 @@ class AMP_Allowed_Tags_Generated {
 					'spec_name' => 'FORM > DIV [submit-success]',
 				),
 			),
+			array(
+				'attr_spec_list' => array(
+					'align' => array(),
+					'submit-success' => array(
+						'mandatory' => true,
+					),
+					'template' => array(
+						'mandatory' => true,
+					),
+				),
+				'tag_spec' => array(
+					'mandatory_parent' => 'form',
+					'spec_name' => 'FORM > DIV [submit-success][template]',
+				),
+			),
 			array(
 				'attr_spec_list' => array(
 					'align' => array(),
 					'submit-error' => array(
-						'dispatch_key' => 1,
 						'mandatory' => true,
 					),
 				),
@@ -2623,6 +3227,21 @@ class AMP_Allowed_Tags_Generated {
 					'spec_name' => 'FORM > DIV [submit-error]',
 				),
 			),
+			array(
+				'attr_spec_list' => array(
+					'align' => array(),
+					'submit-error' => array(
+						'mandatory' => true,
+					),
+					'template' => array(
+						'mandatory' => true,
+					),
+				),
+				'tag_spec' => array(
+					'mandatory_parent' => 'form',
+					'spec_name' => 'FORM > DIV [submit-error][template]',
+				),
+			),
 		),
 		'dl' => array(
 			array(
@@ -4475,11 +5094,12 @@ class AMP_Allowed_Tags_Generated {
 						'value_casei' => 'utf-8',
 					),
 					'color' => array(),
+					'crossorigin' => array(),
 					'href' => array(),
 					'hreflang' => array(),
 					'media' => array(),
 					'rel' => array(
-						'blacklisted_value_regex' => '(^|\\s)(canonical|components|import|manifest|serviceworker|stylesheet|subresource|)(\\s|$)',
+						'blacklisted_value_regex' => '(^|\\s)(canonical|components|import|manifest|preload|serviceworker|stylesheet|subresource|)(\\s|$)',
 						'mandatory' => true,
 					),
 					'sizes' => array(),
@@ -4500,6 +5120,7 @@ class AMP_Allowed_Tags_Generated {
 						'value_casei' => 'utf-8',
 					),
 					'color' => array(),
+					'crossorigin' => array(),
 					'href' => array(
 						'blacklisted_value_regex' => '__amp_source_origin',
 						'mandatory' => true,
@@ -4536,6 +5157,7 @@ class AMP_Allowed_Tags_Generated {
 						'value_casei' => 'utf-8',
 					),
 					'color' => array(),
+					'crossorigin' => array(),
 					'href' => array(
 						'blacklisted_value_regex' => '__amp_source_origin',
 						'mandatory' => true,
@@ -4563,13 +5185,41 @@ class AMP_Allowed_Tags_Generated {
 					'spec_url' => 'https://www.ampproject.org/docs/reference/spec#html-tags',
 				),
 			),
+			array(
+				'attr_spec_list' => array(
+					'as' => array(),
+					'charset' => array(
+						'value_casei' => 'utf-8',
+					),
+					'color' => array(),
+					'crossorigin' => array(),
+					'href' => array(),
+					'hreflang' => array(),
+					'media' => array(),
+					'rel' => array(
+						'dispatch_key' => 2,
+						'mandatory' => true,
+						'value_casei' => 'preload',
+					),
+					'sizes' => array(),
+					'target' => array(),
+					'type' => array(),
+				),
+				'tag_spec' => array(
+					'disallowed_ancestor' => array(
+						'template',
+					),
+					'spec_name' => 'link rel=preload',
+					'spec_url' => 'https://www.ampproject.org/docs/reference/spec#html-tags',
+				),
+			),
 			array(
 				'attr_spec_list' => array(
 					'async' => array(),
 					'crossorigin' => array(),
 					'href' => array(
 						'mandatory' => true,
-						'value_regex' => 'https://cdn\\.materialdesignicons\\.com/([0-9]+\\.?)+/css/materialdesignicons\\.min\\.css|https://cloud\\.typography\\.com/[0-9]*/[0-9]*/css/fonts\\.css|https://fast\\.fonts\\.net/.*|https://fonts\\.googleapis\\.com/css\\?.*|https://fonts\\.googleapis\\.com/icon\\?.*|https://fonts\\.googleapis\\.com/earlyaccess/.*\\.css|https://maxcdn\\.bootstrapcdn\\.com/font-awesome/([0-9]+\\.?)+/css/font-awesome\\.min\\.css(\\?.*)?|https://use\\.typekit\\.net/[\\w\\p{L}\\p{N}_]+\\.css',
+						'value_regex' => 'https://cdn\\.materialdesignicons\\.com/([0-9]+\\.?)+/css/materialdesignicons\\.min\\.css|https://cloud\\.typography\\.com/[0-9]*/[0-9]*/css/fonts\\.css|https://fast\\.fonts\\.net/.*|https://fonts\\.googleapis\\.com/css\\?.*|https://fonts\\.googleapis\\.com/icon\\?.*|https://fonts\\.googleapis\\.com/earlyaccess/.*\\.css|https://maxcdn\\.bootstrapcdn\\.com/font-awesome/([0-9]+\\.?)+/css/font-awesome\\.min\\.css(\\?.*)?|https://use\\.fontawesome\\.com/releases/v([0-9]+\\.?)+/css/(all|brands|solids|fontawesome)\\.css|https://use\\.typekit\\.net/[\\w\\p{L}\\p{N}_]+\\.css',
 					),
 					'integrity' => array(),
 					'media' => array(),
@@ -4594,6 +5244,7 @@ class AMP_Allowed_Tags_Generated {
 						'value_casei' => 'utf-8',
 					),
 					'color' => array(),
+					'crossorigin' => array(),
 					'href' => array(
 						'mandatory' => true,
 					),
@@ -4619,6 +5270,7 @@ class AMP_Allowed_Tags_Generated {
 						'value_casei' => 'utf-8',
 					),
 					'color' => array(),
+					'crossorigin' => array(),
 					'href' => array(
 						'mandatory' => true,
 					),
@@ -4642,6 +5294,7 @@ class AMP_Allowed_Tags_Generated {
 						'value_casei' => 'utf-8',
 					),
 					'color' => array(),
+					'crossorigin' => array(),
 					'href' => array(
 						'mandatory' => true,
 					),
@@ -5033,6 +5686,19 @@ class AMP_Allowed_Tags_Generated {
 					'spec_name' => 'meta name=amp-google-clientid-id-api',
 				),
 			),
+			array(
+				'attr_spec_list' => array(
+					'name' => array(
+						'dispatch_key' => 2,
+						'mandatory' => true,
+						'value_casei' => 'amp-ad-doubleclick-sra',
+					),
+				),
+				'tag_spec' => array(
+					'mandatory_parent' => 'head',
+					'spec_name' => 'meta name=amp-ad-doubleclick-sra',
+				),
+			),
 			array(
 				'attr_spec_list' => array(
 					'content' => array(),
@@ -5041,6 +5707,7 @@ class AMP_Allowed_Tags_Generated {
 						'blacklisted_value_regex' => '(^|\\s)(amp-.*|amp4ads-.*|apple-itunes-app|content-disposition|revisit-after|viewport)(\\s|$)',
 					),
 					'property' => array(),
+					'scheme' => array(),
 				),
 				'tag_spec' => array(
 					'spec_name' => 'meta name= and content=',
@@ -5185,6 +5852,57 @@ class AMP_Allowed_Tags_Generated {
 					'spec_url' => 'https://www.ampproject.org/docs/reference/spec#html-tags',
 				),
 			),
+			array(
+				'attr_spec_list' => array(
+					'content' => array(
+						'mandatory' => true,
+						'value_regex_casei' => '(off|on)',
+					),
+					'http-equiv' => array(
+						'dispatch_key' => 2,
+						'mandatory' => true,
+						'value_casei' => 'x-dns-prefetch-control',
+					),
+				),
+				'tag_spec' => array(
+					'mandatory_ancestor' => 'head',
+					'spec_name' => 'meta http-equiv=x-dns-prefetch-control',
+					'spec_url' => 'https://www.ampproject.org/docs/reference/spec#html-tags',
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'content' => array(
+						'mandatory' => true,
+					),
+					'name' => array(
+						'dispatch_key' => 2,
+						'mandatory' => true,
+						'value_casei' => 'amp-ad-enable-refresh',
+					),
+				),
+				'tag_spec' => array(
+					'mandatory_ancestor' => 'head',
+					'spec_name' => 'meta name=amp-ad-enable-refresh',
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'content' => array(
+						'mandatory' => true,
+					),
+					'name' => array(
+						'dispatch_key' => 2,
+						'mandatory' => true,
+						'value_casei' => 'amp-to-amp-navigation',
+					),
+				),
+				'tag_spec' => array(
+					'mandatory_parent' => 'head',
+					'spec_name' => 'meta name=amp-to-amp-navigation',
+					'unique' => true,
+				),
+			),
 		),
 		'metadata' => array(
 			array(
@@ -6121,6 +6839,31 @@ class AMP_Allowed_Tags_Generated {
 					),
 				),
 			),
+			array(
+				'attr_spec_list' => array(
+					'async' => array(
+						'mandatory' => true,
+						'value' => '',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
+					),
+				),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'name' => 'amp-access-scroll',
+						'requires_usage' => 3,
+					),
+					'requires_extension' => array(
+						'amp-access',
+					),
+				),
+			),
 			array(
 				'attr_spec_list' => array(
 					'async' => array(
@@ -6423,6 +7166,27 @@ class AMP_Allowed_Tags_Generated {
 					),
 				),
 			),
+			array(
+				'attr_spec_list' => array(
+					'async' => array(
+						'mandatory' => true,
+						'value' => '',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
+					),
+				),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'name' => 'amp-beopinion',
+					),
+				),
+			),
 			array(
 				'attr_spec_list' => array(
 					'async' => array(
@@ -6486,9 +7250,325 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-brid-player',
-						'requires_usage' => 2,
+						'name' => 'amp-bodymovin-animation',
+					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'async' => array(
+						'mandatory' => true,
+						'value' => '',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
+					),
+				),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'deprecated_allow_duplicates' => true,
+						'name' => 'amp-brid-player',
+						'requires_usage' => 2,
+					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'async' => array(
+						'mandatory' => true,
+						'value' => '',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
+					),
+				),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'deprecated_allow_duplicates' => true,
+						'name' => 'amp-brightcove',
+						'requires_usage' => 2,
+					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'async' => array(
+						'mandatory' => true,
+						'value' => '',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
+					),
+				),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'name' => 'amp-byside-content',
+					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'async' => array(
+						'mandatory' => true,
+						'value' => '',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
+					),
+				),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'name' => 'amp-call-tracking',
+						'requires_usage' => 2,
+					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'async' => array(
+						'mandatory' => true,
+						'value' => '',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
+					),
+				),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'deprecated_allow_duplicates' => true,
+						'name' => 'amp-carousel',
+						'requires_usage' => 2,
+					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'async' => array(
+						'mandatory' => true,
+						'value' => '',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
+					),
+				),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'name' => 'amp-consent',
+					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'nonce' => array(),
+					'type' => array(
+						'dispatch_key' => 3,
+						'mandatory' => true,
+						'value_casei' => 'application/json',
+					),
+				),
+				'cdata' => array(
+					'blacklisted_cdata_regex' => array(
+						'error_message' => 'html comments',
+						'regex' => '<!--',
+					),
+				),
+				'tag_spec' => array(
+					'mandatory_parent' => 'amp-consent',
+					'requires_extension' => array(
+						'amp-consent',
+					),
+					'spec_name' => 'amp-consent extension .json script',
+					'unique' => true,
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'async' => array(
+						'mandatory' => true,
+						'value' => '',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
+					),
+				),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'deprecated_allow_duplicates' => true,
+						'name' => 'amp-dailymotion',
+						'requires_usage' => 2,
+					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'async' => array(
+						'mandatory' => true,
+						'value' => '',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
+					),
+				),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'name' => 'amp-date-picker',
+					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'name' => 'amp-document-recommendations',
+					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'recommendations' => array(
+						'dispatch_key' => 3,
+						'mandatory' => true,
+						'value_casei' => 'application/json',
+					),
+				),
+				'tag_spec' => array(
+					'mandatory_parent' => 'amp-document-recommendations',
+					'requires_extension' => array(
+						'amp-document-recommendations',
+					),
+					'spec_name' => 'amp-document-recommendations extension .json configuration',
+					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-document-recommendations',
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'async' => array(
+						'mandatory' => true,
+						'value' => '',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
+					),
+				),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'deprecated_allow_duplicates' => true,
+						'name' => 'amp-dynamic-css-classes',
+						'requires_usage' => 3,
+					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'async' => array(
+						'mandatory' => true,
+						'value' => '',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
+					),
+				),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'deprecated_allow_duplicates' => true,
+						'name' => 'amp-experiment',
+						'requires_usage' => 2,
+					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'nonce' => array(),
+					'type' => array(
+						'dispatch_key' => 3,
+						'mandatory' => true,
+						'value_casei' => 'application/json',
+					),
+				),
+				'cdata' => array(
+					'blacklisted_cdata_regex' => array(
+						'error_message' => 'html comments',
+						'regex' => '<!--',
+					),
+				),
+				'tag_spec' => array(
+					'mandatory_parent' => 'amp-experiment',
+					'spec_name' => 'amp-experiment extension .json script',
+					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-experiment',
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'async' => array(
+						'mandatory' => true,
+						'value' => '',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
+					),
+				),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'name' => 'amp-facebook-comments',
 					),
 				),
 			),
@@ -6509,9 +7589,7 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-brightcove',
-						'requires_usage' => 2,
+						'name' => 'amp-facebook-like',
 					),
 				),
 			),
@@ -6532,8 +7610,7 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-call-tracking',
-						'requires_usage' => 2,
+						'name' => 'amp-facebook-page',
 					),
 				),
 			),
@@ -6555,7 +7632,7 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-carousel',
+						'name' => 'amp-facebook',
 						'requires_usage' => 2,
 					),
 				),
@@ -6578,7 +7655,7 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-dailymotion',
+						'name' => 'amp-fit-text',
 						'requires_usage' => 2,
 					),
 				),
@@ -6601,8 +7678,8 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-dynamic-css-classes',
-						'requires_usage' => 3,
+						'name' => 'amp-font',
+						'requires_usage' => 2,
 					),
 				),
 			),
@@ -6624,30 +7701,31 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-experiment',
+						'name' => 'amp-form',
 						'requires_usage' => 2,
 					),
 				),
 			),
 			array(
 				'attr_spec_list' => array(
-					'nonce' => array(),
-					'type' => array(
-						'dispatch_key' => 3,
+					'async' => array(
 						'mandatory' => true,
-						'value_casei' => 'application/json',
+						'value' => '',
 					),
-				),
-				'cdata' => array(
-					'blacklisted_cdata_regex' => array(
-						'error_message' => 'html comments',
-						'regex' => '<!--',
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
 					),
 				),
 				'tag_spec' => array(
-					'mandatory_parent' => 'amp-experiment',
-					'spec_name' => 'amp-experiment extension .json script',
-					'spec_url' => 'https://www.ampproject.org/docs/reference/components/amp-experiment',
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'name' => 'amp-fx-collection',
+						'requires_usage' => 3,
+					),
 				),
 			),
 			array(
@@ -6667,7 +7745,9 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-facebook-comments',
+						'deprecated_allow_duplicates' => true,
+						'name' => 'amp-fx-flying-carpet',
+						'requires_usage' => 2,
 					),
 				),
 			),
@@ -6688,7 +7768,9 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-facebook-like',
+						'deprecated_allow_duplicates' => true,
+						'name' => 'amp-gfycat',
+						'requires_usage' => 2,
 					),
 				),
 			),
@@ -6709,9 +7791,7 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-facebook',
-						'requires_usage' => 2,
+						'name' => 'amp-gist',
 					),
 				),
 			),
@@ -6732,9 +7812,7 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-fit-text',
-						'requires_usage' => 2,
+						'name' => 'amp-hulu',
 					),
 				),
 			),
@@ -6756,7 +7834,7 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-font',
+						'name' => 'amp-iframe',
 						'requires_usage' => 2,
 					),
 				),
@@ -6778,9 +7856,7 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-form',
-						'requires_usage' => 2,
+						'name' => 'amp-ima-video',
 					),
 				),
 			),
@@ -6802,7 +7878,7 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-fx-flying-carpet',
+						'name' => 'amp-image-lightbox',
 						'requires_usage' => 2,
 					),
 				),
@@ -6824,9 +7900,7 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-gfycat',
-						'requires_usage' => 2,
+						'name' => 'amp-imgur',
 					),
 				),
 			),
@@ -6847,7 +7921,9 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-gist',
+						'deprecated_allow_duplicates' => true,
+						'name' => 'amp-instagram',
+						'requires_usage' => 2,
 					),
 				),
 			),
@@ -6868,7 +7944,9 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-hulu',
+						'deprecated_allow_duplicates' => true,
+						'name' => 'amp-install-serviceworker',
+						'requires_usage' => 2,
 					),
 				),
 			),
@@ -6889,8 +7967,7 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-iframe',
+						'name' => 'amp-izlesene',
 						'requires_usage' => 2,
 					),
 				),
@@ -6912,7 +7989,9 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-ima-video',
+						'deprecated_allow_duplicates' => true,
+						'name' => 'amp-jwplayer',
+						'requires_usage' => 2,
 					),
 				),
 			),
@@ -6934,7 +8013,7 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-image-lightbox',
+						'name' => 'amp-kaltura-player',
 						'requires_usage' => 2,
 					),
 				),
@@ -6956,7 +8035,8 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-imgur',
+						'name' => 'amp-lightbox-gallery',
+						'requires_usage' => 3,
 					),
 				),
 			),
@@ -6978,7 +8058,7 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-instagram',
+						'name' => 'amp-lightbox',
 						'requires_usage' => 2,
 					),
 				),
@@ -7001,7 +8081,7 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-install-serviceworker',
+						'name' => 'amp-list',
 						'requires_usage' => 2,
 					),
 				),
@@ -7023,9 +8103,11 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-izlesene',
+						'name' => 'amp-live-list',
 						'requires_usage' => 2,
 					),
+					'mandatory_parent' => 'head',
+					'unique_warning' => true,
 				),
 			),
 			array(
@@ -7045,9 +8127,7 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-jwplayer',
-						'requires_usage' => 2,
+						'name' => 'amp-mathml',
 					),
 				),
 			),
@@ -7069,7 +8149,8 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-kaltura-player',
+						'is_custom_template' => true,
+						'name' => 'amp-mustache',
 						'requires_usage' => 2,
 					),
 				),
@@ -7091,9 +8172,7 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-lightbox',
-						'requires_usage' => 2,
+						'name' => 'amp-nexxtv-player',
 					),
 				),
 			),
@@ -7115,7 +8194,7 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-list',
+						'name' => 'amp-o2-player',
 						'requires_usage' => 2,
 					),
 				),
@@ -7137,11 +8216,8 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-live-list',
-						'requires_usage' => 2,
+						'name' => 'amp-ooyala-player',
 					),
-					'mandatory_parent' => 'head',
-					'unique_warning' => true,
 				),
 			),
 			array(
@@ -7162,8 +8238,7 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'is_custom_template' => true,
-						'name' => 'amp-mustache',
+						'name' => 'amp-pinterest',
 						'requires_usage' => 2,
 					),
 				),
@@ -7185,7 +8260,7 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-nexxtv-player',
+						'name' => 'amp-playbuzz',
 					),
 				),
 			),
@@ -7206,9 +8281,7 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-o2-player',
-						'requires_usage' => 2,
+						'name' => 'amp-position-observer',
 					),
 				),
 			),
@@ -7229,7 +8302,9 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-ooyala-player',
+						'deprecated_allow_duplicates' => true,
+						'name' => 'amp-reach-player',
+						'requires_usage' => 2,
 					),
 				),
 			),
@@ -7251,8 +8326,7 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-pinterest',
-						'requires_usage' => 2,
+						'name' => 'amp-reddit',
 					),
 				),
 			),
@@ -7273,7 +8347,7 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-playbuzz',
+						'name' => 'amp-riddle-quiz',
 					),
 				),
 			),
@@ -7294,7 +8368,8 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-position-observer',
+						'name' => 'amp-selector',
+						'requires_usage' => 2,
 					),
 				),
 			),
@@ -7316,7 +8391,7 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-reach-player',
+						'name' => 'amp-sidebar',
 						'requires_usage' => 2,
 					),
 				),
@@ -7339,7 +8414,8 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-reddit',
+						'name' => 'amp-social-share',
+						'requires_usage' => 2,
 					),
 				),
 			),
@@ -7360,7 +8436,8 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-selector',
+						'deprecated_allow_duplicates' => true,
+						'name' => 'amp-soundcloud',
 						'requires_usage' => 2,
 					),
 				),
@@ -7383,7 +8460,7 @@ class AMP_Allowed_Tags_Generated {
 							'latest',
 						),
 						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-sidebar',
+						'name' => 'amp-springboard-player',
 						'requires_usage' => 2,
 					),
 				),
@@ -7403,10 +8480,13 @@ class AMP_Allowed_Tags_Generated {
 					'extension_spec' => array(
 						'allowed_versions' => array(
 							'0.1',
+							'1.0',
 							'latest',
 						),
-						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-social-share',
+						'deprecated_versions' => array(
+							'0.1',
+						),
+						'name' => 'amp-sticky-ad',
 						'requires_usage' => 2,
 					),
 				),
@@ -7428,10 +8508,32 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-soundcloud',
-						'requires_usage' => 2,
+						'name' => 'amp-story-auto-ads',
+					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'nonce' => array(),
+					'type' => array(
+						'dispatch_key' => 3,
+						'mandatory' => true,
+						'value_casei' => 'application/json',
+					),
+				),
+				'cdata' => array(
+					'blacklisted_cdata_regex' => array(
+						'error_message' => 'html comments',
+						'regex' => '<!--',
+					),
+				),
+				'tag_spec' => array(
+					'mandatory_parent' => 'amp-story-auto-ads',
+					'requires_extension' => array(
+						'amp-story-auto-ads',
 					),
+					'spec_name' => 'amp-story-auto-ads config script',
+					'spec_url' => 'https://github.com/ampproject/amphtml/blob/master/extensions/amp-story/amp-story-auto-ads.md',
 				),
 			),
 			array(
@@ -7451,9 +8553,7 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'deprecated_allow_duplicates' => true,
-						'name' => 'amp-springboard-player',
-						'requires_usage' => 2,
+						'name' => 'amp-story',
 					),
 				),
 			),
@@ -7472,15 +8572,39 @@ class AMP_Allowed_Tags_Generated {
 					'extension_spec' => array(
 						'allowed_versions' => array(
 							'0.1',
-							'1.0',
 							'latest',
 						),
-						'deprecated_versions' => array(
-							'0.1',
-						),
-						'name' => 'amp-sticky-ad',
-						'requires_usage' => 2,
+						'name' => 'amp-subscriptions',
+						'requires_usage' => 3,
+					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'id' => array(
+						'dispatch_key' => 2,
+						'mandatory' => true,
+						'value' => 'amp-subscriptions',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'mandatory' => true,
+						'value_casei' => 'application/json',
+					),
+				),
+				'cdata' => array(
+					'blacklisted_cdata_regex' => array(
+						'error_message' => 'html comments',
+						'regex' => '<!--',
+					),
+				),
+				'tag_spec' => array(
+					'mandatory_parent' => 'head',
+					'requires_extension' => array(
+						'amp-subscriptions',
 					),
+					'spec_name' => 'amp-subscriptions extension .json script',
+					'unique' => true,
 				),
 			),
 			array(
@@ -7500,7 +8624,11 @@ class AMP_Allowed_Tags_Generated {
 							'0.1',
 							'latest',
 						),
-						'name' => 'amp-story',
+						'name' => 'amp-subscriptions-google',
+						'requires_usage' => 3,
+					),
+					'requires_extension' => array(
+						'amp-subscriptions',
 					),
 				),
 			),
@@ -7682,6 +8810,27 @@ class AMP_Allowed_Tags_Generated {
 					),
 				),
 			),
+			array(
+				'attr_spec_list' => array(
+					'async' => array(
+						'mandatory' => true,
+						'value' => '',
+					),
+					'nonce' => array(),
+					'type' => array(
+						'value_casei' => 'text/javascript',
+					),
+				),
+				'tag_spec' => array(
+					'extension_spec' => array(
+						'allowed_versions' => array(
+							'0.1',
+							'latest',
+						),
+						'name' => 'amp-wistia-player',
+					),
+				),
+			),
 			array(
 				'attr_spec_list' => array(
 					'async' => array(
@@ -8410,10 +9559,28 @@ class AMP_Allowed_Tags_Generated {
 				'tag_spec' => array(
 					'disallowed_ancestor' => array(
 						'template',
+						'amp-story-auto-ads',
+						'form > div [submit-success][template]',
+						'form > div [submit-error][template]',
+					),
+					'requires_extension' => array(
+						'amp-mustache',
 					),
+				),
+			),
+			array(
+				'attr_spec_list' => array(
+					'type' => array(
+						'mandatory' => true,
+						'value' => 'amp-mustache',
+					),
+				),
+				'tag_spec' => array(
+					'mandatory_parent' => 'amp-story-auto-ads',
 					'requires_extension' => array(
 						'amp-mustache',
 					),
+					'spec_name' => 'amp-story-auto-ads > template',
 				),
 			),
 		),
@@ -9459,6 +10626,9 @@ class AMP_Allowed_Tags_Generated {
 		'amp-access-show' => array(),
 		'amp-access-style' => array(),
 		'amp-access-template' => array(),
+		'amp-fx' => array(
+			'value_casei' => 'parallax',
+		),
 		'aria-activedescendant' => array(),
 		'aria-atomic' => array(),
 		'aria-autocomplete' => array(),
@@ -9533,6 +10703,18 @@ class AMP_Allowed_Tags_Generated {
 		'resource' => array(),
 		'rev' => array(),
 		'role' => array(),
+		'subscriptions-action' => array(),
+		'subscriptions-actions' => array(
+			'value' => '',
+		),
+		'subscriptions-dialog' => array(
+			'value' => '',
+		),
+		'subscriptions-display' => array(),
+		'subscriptions-section' => array(
+			'value_regex_casei' => '(actions|content|content-not-granted)',
+		),
+		'subscriptions-service' => array(),
 		'tabindex' => array(),
 		'title' => array(),
 		'translate' => array(),
diff --git a/includes/sanitizers/class-amp-base-sanitizer.php b/includes/sanitizers/class-amp-base-sanitizer.php
index 8e7a936afb7..0fc9a697085 100644
--- a/includes/sanitizers/class-amp-base-sanitizer.php
+++ b/includes/sanitizers/class-amp-base-sanitizer.php
@@ -48,6 +48,14 @@ abstract class AMP_Base_Sanitizer {
 	 *      @type string[] $amp_allowed_tags
 	 *      @type string[] $amp_globally_allowed_attributes
 	 *      @type string[] $amp_layout_allowed_attributes
+	 *      @type array $amp_allowed_tags
+	 *      @type array $amp_globally_allowed_attributes
+	 *      @type array $amp_layout_allowed_attributes
+	 *      @type array $amp_bind_placeholder_prefix
+	 *      @type bool $allow_dirty_styles
+	 *      @type bool $allow_dirty_scripts
+	 *      @type bool $disable_invalid_removal
+	 *      @type callable $remove_invalid_callback
 	 * }
 	 */
 	protected $args;
@@ -167,12 +175,15 @@ protected function get_body_node() {
 	 * @return float|int|string Returns a numeric dimension value, or an empty string.
 	 */
 	public function sanitize_dimension( $value, $dimension ) {
-		if ( empty( $value ) ) {
+
+		// Allows 0 to be used as valid dimension.
+		if ( null === $value ) {
 			return '';
 		}
 
-		if ( false !== filter_var( $value, FILTER_VALIDATE_INT ) ) {
-			return absint( $value );
+		// Accepts both integers and floats & prevents negative values.
+		if ( is_numeric( $value ) ) {
+			return max( 0, floatval( $value ) );
 		}
 
 		if ( AMP_String_Utils::endswith( $value, 'px' ) ) {
@@ -190,7 +201,7 @@ public function sanitize_dimension( $value, $dimension ) {
 	}
 
 	/**
-	 * Enforce fixed height.
+	 * Sets the layout, and possibly the 'height' and 'width' attributes.
 	 *
 	 * @param string[] $attributes {
 	 *      Attributes.
@@ -203,12 +214,11 @@ public function sanitize_dimension( $value, $dimension ) {
 	 * }
 	 * @return string[]
 	 */
-	public function enforce_fixed_height( $attributes ) {
+	public function set_layout( $attributes ) {
 		if ( empty( $attributes['height'] ) ) {
 			unset( $attributes['width'] );
 			$attributes['height'] = self::FALLBACK_HEIGHT;
 		}
-
 		if ( empty( $attributes['width'] ) ) {
 			$attributes['layout'] = 'fixed-height';
 		}
@@ -216,42 +226,6 @@ public function enforce_fixed_height( $attributes ) {
 		return $attributes;
 	}
 
-	/**
-	 * This is our workaround to enforce max sizing with layout=responsive.
-	 *
-	 * We want elements to not grow beyond their width and shrink to fill the screen on viewports smaller than their width.
-	 *
-	 * See https://github.com/ampproject/amphtml/issues/1280#issuecomment-171533526
-	 * See https://github.com/Automattic/amp-wp/issues/101
-	 *
-	 * @param string[] $attributes {
-	 *      Attributes.
-	 *
-	 *      @type int $height
-	 *      @type int $width
-	 *      @type string $sizes
-	 *      @type string $class
-	 *      @type string $layout
-	 * }
-	 * @return string[]
-	 */
-	public function enforce_sizes_attribute( $attributes ) {
-		if ( ! isset( $attributes['width'], $attributes['height'] ) ) {
-			return $attributes;
-		}
-
-		$max_width = $attributes['width'];
-		if ( isset( $this->args['content_max_width'] ) && $max_width >= $this->args['content_max_width'] ) {
-			$max_width = $this->args['content_max_width'];
-		}
-
-		$attributes['sizes'] = sprintf( '(min-width: %1$dpx) %1$dpx, 100vw', absint( $max_width ) );
-
-		$this->add_or_append_attribute( $attributes, 'class', 'amp-wp-enforced-sizes' );
-
-		return $attributes;
-	}
-
 	/**
 	 * Adds or appends key and value to list of attributes
 	 *
@@ -313,13 +287,19 @@ public function maybe_enforce_https_src( $src, $force_https = false ) {
 	 *
 	 * @since 0.7
 	 *
-	 * @param DOMElement $child The node to remove.
-	 * @return void.
+	 * @param DOMNode|DOMElement $node The node to remove.
+	 * @param array              $args Additional args to pass to validation error callback.
+	 *
+	 * @return void
 	 */
-	public function remove_invalid_child( $child ) {
-		$child->parentNode->removeChild( $child );
-		if ( isset( $this->args['remove_invalid_callback'] ) ) {
-			call_user_func( $this->args['remove_invalid_callback'], $child, AMP_Validation_Utils::NODE_REMOVED );
+	public function remove_invalid_child( $node, $args = array() ) {
+		if ( isset( $this->args['validation_error_callback'] ) ) {
+			call_user_func( $this->args['validation_error_callback'],
+				array_merge( compact( 'node' ), $args )
+			);
+		}
+		if ( empty( $this->args['disable_invalid_removal'] ) ) {
+			$node->parentNode->removeChild( $node );
 		}
 	}
 
@@ -331,15 +311,35 @@ public function remove_invalid_child( $child ) {
 	 *
 	 * @since 0.7
 	 *
-	 * @param DOMElement $element   The node for which to remove the attribute.
-	 * @param string     $attribute The attribute to remove from the node.
-	 * @return void.
+	 * @param DOMElement     $element   The node for which to remove the attribute.
+	 * @param DOMAttr|string $attribute The attribute to remove from the element.
+	 * @param array          $args      Additional args to pass to validation error callback.
+	 * @return void
 	 */
-	public function remove_invalid_attribute( $element, $attribute ) {
-		$element->removeAttribute( $attribute );
-		if ( isset( $this->args['remove_invalid_callback'] ) ) {
-			call_user_func( $this->args['remove_invalid_callback'], $element, AMP_Validation_Utils::ATTRIBUTE_REMOVED, $attribute );
+	public function remove_invalid_attribute( $element, $attribute, $args = array() ) {
+		if ( isset( $this->args['validation_error_callback'] ) ) {
+			if ( is_string( $attribute ) ) {
+				$attribute = $element->getAttributeNode( $attribute );
+			}
+			if ( $attribute ) {
+				call_user_func( $this->args['validation_error_callback'],
+					array_merge(
+						array(
+							'node' => $attribute,
+						),
+						$args
+					)
+				);
+				if ( empty( $this->args['disable_invalid_removal'] ) ) {
+					$element->removeAttributeNode( $attribute );
+				}
+			}
+		} elseif ( empty( $this->args['disable_invalid_removal'] ) ) {
+			if ( is_string( $attribute ) ) {
+				$element->removeAttribute( $attribute );
+			} else {
+				$element->removeAttributeNode( $attribute );
+			}
 		}
 	}
-
 }
diff --git a/includes/sanitizers/class-amp-iframe-sanitizer.php b/includes/sanitizers/class-amp-iframe-sanitizer.php
index 9dac35a8a3e..07c07875f72 100644
--- a/includes/sanitizers/class-amp-iframe-sanitizer.php
+++ b/includes/sanitizers/class-amp-iframe-sanitizer.php
@@ -79,9 +79,11 @@ public function sanitize() {
 			}
 
 			$this->did_convert_elements = true;
-
-			$new_attributes = $this->enforce_fixed_height( $new_attributes );
-			$new_attributes = $this->enforce_sizes_attribute( $new_attributes );
+			$new_attributes             = $this->set_layout( $new_attributes );
+			if ( empty( $new_attributes['layout'] ) && ! empty( $new_attributes['width'] ) && ! empty( $new_attributes['height'] ) ) {
+				$new_attributes['layout'] = 'intrinsic';
+				$this->add_or_append_attribute( $new_attributes, 'class', 'amp-wp-enforced-sizes' );
+			}
 
 			$new_node = AMP_DOM_Utils::create_node( $this->dom, 'amp-iframe', $new_attributes );
 
@@ -126,8 +128,7 @@ public function sanitize() {
 	 * @return array Returns HTML attributes; removes any not specifically declared above from input.
 	 */
 	private function filter_attributes( $attributes ) {
-		$out          = array();
-		$out['style'] = 'max-width:100%'; // AMP_Style_Sanitizer will move this to the amp-custom style.
+		$out = array();
 
 		foreach ( $attributes as $name => $value ) {
 			switch ( $name ) {
diff --git a/includes/sanitizers/class-amp-img-sanitizer.php b/includes/sanitizers/class-amp-img-sanitizer.php
index 971e8d6cdec..e3fa9a878c3 100644
--- a/includes/sanitizers/class-amp-img-sanitizer.php
+++ b/includes/sanitizers/class-amp-img-sanitizer.php
@@ -73,13 +73,13 @@ public function sanitize() {
 				continue;
 			}
 
-			if ( ! $node->hasAttribute( 'src' ) || '' === $node->getAttribute( 'src' ) ) {
+			if ( ! $node->hasAttribute( 'src' ) || '' === trim( $node->getAttribute( 'src' ) ) ) {
 				$this->remove_invalid_child( $node );
 				continue;
 			}
 
 			// Determine which images need their dimensions determined/extracted.
-			if ( '' === $node->getAttribute( 'width' ) || '' === $node->getAttribute( 'height' ) ) {
+			if ( ! is_numeric( $node->getAttribute( 'width' ) ) || ! is_numeric( $node->getAttribute( 'height' ) ) ) {
 				$need_dimensions[ $node->getAttribute( 'src' ) ][] = $node;
 			} else {
 				$this->adjust_and_replace_node( $node );
@@ -119,7 +119,6 @@ private function filter_attributes( $attributes ) {
 				case 'alt':
 				case 'class':
 				case 'srcset':
-				case 'sizes':
 				case 'on':
 				case 'attribution':
 					$out[ $name ] = $value;
@@ -130,6 +129,10 @@ private function filter_attributes( $attributes ) {
 					$out[ $name ] = $this->sanitize_dimension( $value, $name );
 					break;
 
+				case 'data-amp-layout':
+					$out['layout'] = $value;
+					break;
+
 				default:
 					break;
 			}
@@ -154,18 +157,30 @@ private function determine_dimensions( $need_dimensions ) {
 				if ( ! $node instanceof DOMElement ) {
 					continue;
 				}
-
-				// Provide default dimensions for images whose dimensions we couldn't fetch.
-				if ( false !== $dimensions ) {
-					$node->setAttribute( 'width', $dimensions['width'] );
-					$node->setAttribute( 'height', $dimensions['height'] );
-				} else {
-					$width  = isset( $this->args['content_max_width'] ) ? $this->args['content_max_width'] : self::FALLBACK_WIDTH;
+				if (
+					! is_numeric( $node->getAttribute( 'width' ) ) &&
+					! is_numeric( $node->getAttribute( 'height' ) )
+				) {
 					$height = self::FALLBACK_HEIGHT;
+					$width  = self::FALLBACK_WIDTH;
 					$node->setAttribute( 'width', $width );
 					$node->setAttribute( 'height', $height );
 					$class = $node->hasAttribute( 'class' ) ? $node->getAttribute( 'class' ) . ' amp-wp-unknown-size' : 'amp-wp-unknown-size';
 					$node->setAttribute( 'class', $class );
+				} elseif (
+					! is_numeric( $node->getAttribute( 'height' ) )
+				) {
+					$height = self::FALLBACK_HEIGHT;
+					$node->setAttribute( 'height', $height );
+					$class = $node->hasAttribute( 'class' ) ? $node->getAttribute( 'class' ) . ' amp-wp-unknown-size amp-wp-unknown-height' : 'amp-wp-unknown-size amp-wp-unknown-height';
+					$node->setAttribute( 'class', $class );
+				} elseif (
+					! is_numeric( $node->getAttribute( 'width' ) )
+				) {
+					$width = self::FALLBACK_WIDTH;
+					$node->setAttribute( 'width', $width );
+					$class = $node->hasAttribute( 'class' ) ? $node->getAttribute( 'class' ) . ' amp-wp-unknown-size amp-wp-unknown-width' : 'amp-wp-unknown-size amp-wp-unknown-width';
+					$node->setAttribute( 'class', $class );
 				}
 			}
 		}
@@ -192,7 +207,10 @@ private function adjust_and_replace_nodes_in_array_map( $node_lists ) {
 	private function adjust_and_replace_node( $node ) {
 		$old_attributes = AMP_DOM_Utils::get_node_attributes_as_assoc_array( $node );
 		$new_attributes = $this->filter_attributes( $old_attributes );
-		$new_attributes = $this->enforce_sizes_attribute( $new_attributes );
+		$this->add_or_append_attribute( $new_attributes, 'class', 'amp-wp-enforced-sizes' );
+		if ( empty( $new_attributes['layout'] ) && ! empty( $new_attributes['height'] ) && ! empty( $new_attributes['width'] ) ) {
+			$new_attributes['layout'] = 'intrinsic';
+		}
 		if ( $this->is_gif_url( $new_attributes['src'] ) ) {
 			$this->did_convert_elements = true;
 
diff --git a/includes/sanitizers/class-amp-style-sanitizer.php b/includes/sanitizers/class-amp-style-sanitizer.php
index 92e9831d454..fe07b47e46c 100644
--- a/includes/sanitizers/class-amp-style-sanitizer.php
+++ b/includes/sanitizers/class-amp-style-sanitizer.php
@@ -15,9 +15,10 @@ class AMP_Style_Sanitizer extends AMP_Base_Sanitizer {
 	/**
 	 * Styles.
 	 *
-	 * @var string[] List of CSS styles in HTML content of DOMDocument ($this->dom).
+	 * List of CSS styles in HTML content of DOMDocument ($this->dom).
 	 *
 	 * @since 0.4
+	 * @var array[]
 	 */
 	private $styles = array();
 
@@ -47,6 +48,15 @@ class AMP_Style_Sanitizer extends AMP_Base_Sanitizer {
 	 */
 	private $custom_max_size;
 
+	/**
+	 * Current CSS size.
+	 *
+	 * Sum of CSS located in $styles and $stylesheets.
+	 *
+	 * @var int
+	 */
+	private $current_custom_size = 0;
+
 	/**
 	 * The style[amp-custom] element.
 	 *
@@ -125,7 +135,7 @@ public function __construct( DOMDocument $dom, array $args = array() ) {
 	 *
 	 * @since 0.4
 	 *
-	 * @return string[] Mapping CSS selectors to array of properties, or mapping of keys starting with 'stylesheet:' with value being the stylesheet.
+	 * @return array[] Mapping CSS selectors to array of properties, or mapping of keys starting with 'stylesheet:' with value being the stylesheet.
 	 */
 	public function get_styles() {
 		if ( ! $this->did_convert_elements ) {
@@ -152,6 +162,11 @@ public function get_stylesheets() {
 	public function sanitize() {
 		$elements = array();
 
+		// Do nothing if inline styles are allowed.
+		if ( ! empty( $this->args['allow_dirty_styles'] ) ) {
+			return;
+		}
+
 		/*
 		 * Note that xpath is used to query the DOM so that the link and style elements will be
 		 * in document order. DOMNode::compareDocumentPosition() is not yet implemented.
@@ -204,22 +219,7 @@ public function sanitize() {
 				$head->appendChild( $this->amp_custom_style_element );
 			}
 
-			// Gather stylesheets to print as long as they don't surpass the limit.
-			$skipped    = array();
-			$css        = '';
-			$total_size = 0;
-			foreach ( $this->get_stylesheets() as $key => $stylesheet ) {
-				$sheet_size = strlen( $stylesheet );
-				if ( $total_size + $sheet_size > $this->custom_max_size ) {
-					$skipped[] = $key;
-				} else {
-					if ( $total_size ) {
-						$css .= ' ';
-					}
-					$css        .= $stylesheet;
-					$total_size += $sheet_size;
-				}
-			}
+			$css = implode( '', $this->get_stylesheets() );
 
 			/*
 			 * Let the style[amp-custom] be populated with the concatenated CSS.
@@ -231,15 +231,6 @@ public function sanitize() {
 				$this->amp_custom_style_element->removeChild( $this->amp_custom_style_element->firstChild );
 			}
 			$this->amp_custom_style_element->appendChild( $this->dom->createTextNode( $css ) );
-
-			// @todo This would be a candidate for sanitization reporting.
-			// Add comments to indicate which sheets were not included.
-			foreach ( array_reverse( $skipped ) as $skip ) {
-				$this->amp_custom_style_element->parentNode->insertBefore(
-					$this->dom->createComment( sprintf( 'Skipped including %s stylesheet since too large.', $skip ) ),
-					$this->amp_custom_style_element->nextSibling
-				);
-			}
 		}
 	}
 
@@ -298,18 +289,30 @@ public function get_validated_css_file_path( $src ) {
 	 * @param DOMElement $element Style element.
 	 */
 	private function process_style_element( DOMElement $element ) {
-		if ( 'body' === $element->parentNode->nodeName && $element->hasAttribute( 'amp-keyframes' ) ) {
+		if ( $element->hasAttribute( 'amp-keyframes' ) ) {
 			$validity = $this->validate_amp_keyframe( $element );
-			if ( true !== $validity ) {
-				$element->parentNode->removeChild( $element ); // @todo Add reporting.
+			if ( is_wp_error( $validity ) ) {
+				$this->remove_invalid_child( $element, array(
+					'message' => $validity->get_error_message(),
+				) );
 			}
 			return;
 		}
 
 		$rules = trim( $element->textContent );
-		$rules = $this->remove_illegal_css( $rules );
+		$rules = $this->remove_illegal_css( $rules, $element );
+
+		// Remove if surpasses max size.
+		$length = strlen( $rules );
+		if ( $this->current_custom_size + $length > $this->custom_max_size ) {
+			$this->remove_invalid_child( $element, array(
+				'message' => __( 'Too much CSS enqueued.', 'amp' ),
+			) );
+			return;
+		}
 
 		$this->stylesheets[ md5( $rules ) ] = $rules;
+		$this->current_custom_size         += $length;
 
 		if ( $element->hasAttribute( 'amp-custom' ) ) {
 			if ( ! $this->amp_custom_style_element ) {
@@ -339,22 +342,34 @@ private function process_link_element( DOMElement $element ) {
 
 		$css_file_path = $this->get_validated_css_file_path( $href );
 		if ( is_wp_error( $css_file_path ) ) {
-			$element->parentNode->removeChild( $element ); // @todo Report removal. Show HTML comment?
+			$this->remove_invalid_child( $element, array(
+				'message' => $css_file_path->get_error_message(),
+			) );
 			return;
 		}
 
 		// Load the CSS from the filesystem.
-		$css  = "\n/* $href */\n";
-		$css .= file_get_contents( $css_file_path ); // phpcs:ignore -- It's a local filesystem path not a remote request.
+		$rules  = "\n/* $href */\n";
+		$rules .= file_get_contents( $css_file_path ); // phpcs:ignore -- It's a local filesystem path not a remote request.
 
-		$css = $this->remove_illegal_css( $css );
+		$rules = $this->remove_illegal_css( $rules, $element );
 
 		$media = $element->getAttribute( 'media' );
 		if ( $media && 'all' !== $media ) {
-			$css = sprintf( '@media %s { %s }', $media, $css );
+			$rules = sprintf( '@media %s { %s }', $media, $rules );
 		}
 
-		$this->stylesheets[ $href ] = $css;
+		// Remove if surpasses max size.
+		$length = strlen( $rules );
+		if ( $this->current_custom_size + $length > $this->custom_max_size ) {
+			$this->remove_invalid_child( $element, array(
+				'message' => __( 'Too much CSS enqueued.', 'amp' ),
+			) );
+			return;
+		}
+
+		$this->current_custom_size += $length;
+		$this->stylesheets[ $href ] = $rules;
 
 		// Remove now that styles have been processed.
 		$element->parentNode->removeChild( $element );
@@ -367,12 +382,25 @@ private function process_link_element( DOMElement $element ) {
 	 *
 	 * @todo This needs proper CSS parser and to take an alternative approach to removing !important by extracting
 	 * the rule into a separate style rule with a very specific selector.
-	 * @param string $stylesheet Stylesheet.
+	 * @param string     $stylesheet Stylesheet.
+	 * @param DOMElement $element    Element where the stylesheet came from.
 	 * @return string Scrubbed stylesheet.
 	 */
-	private function remove_illegal_css( $stylesheet ) {
-		$stylesheet = preg_replace( '/\s*!important/', '', $stylesheet ); // Note this has to also replace inside comments to be valid.
-		$stylesheet = preg_replace( '/overflow\s*:\s*(auto|scroll)\s*;?\s*/', '', $stylesheet );
+	private function remove_illegal_css( $stylesheet, $element ) {
+		$stylesheet = preg_replace( '/\s*!important/', '', $stylesheet, -1, $important_count ); // Note this has to also replace inside comments to be valid.
+		if ( $important_count > 0 && ! empty( $this->args['validation_error_callback'] ) ) {
+			call_user_func( $this->args['validation_error_callback'], array(
+				'code' => 'css_important_removed',
+				'node' => $element,
+			) );
+		}
+		$stylesheet = preg_replace( '/overflow(-[xy])?\s*:\s*(auto|scroll)\s*;?\s*/', '', $stylesheet, -1, $overlow_count );
+		if ( $overlow_count > 0 && ! empty( $this->args['validation_error_callback'] ) ) {
+			call_user_func( $this->args['validation_error_callback'], array(
+				'code' => 'css_overflow_property_removed',
+				'node' => $element,
+			) );
+		}
 		return $stylesheet;
 	}
 
@@ -386,15 +414,19 @@ private function remove_illegal_css( $stylesheet ) {
 	 * @return true|WP_Error Validity.
 	 */
 	private function validate_amp_keyframe( $style ) {
+		if ( 'body' !== $style->parentNode->nodeName ) {
+			return new WP_Error( 'mandatory_body_child', __( 'amp-keyframes is not child of body element.', 'amp' ) );
+		}
+
 		if ( $this->keyframes_max_size && strlen( $style->textContent ) > $this->keyframes_max_size ) {
-			return new WP_Error( 'max_bytes' );
+			return new WP_Error( 'max_bytes', __( 'amp-keyframes is too large', 'amp' ) );
 		}
 
 		// This logic could be in AMP_Tag_And_Attribute_Sanitizer, but since it only applies to amp-keyframes it seems unnecessary.
 		$next_sibling = $style->nextSibling;
 		while ( $next_sibling ) {
 			if ( $next_sibling instanceof DOMElement ) {
-				return new WP_Error( 'mandatory_last_child' );
+				return new WP_Error( 'mandatory_last_child', __( 'amp-keyframes is not last element in body.', 'amp' ) );
 			}
 			$next_sibling = $next_sibling->nextSibling;
 		}
@@ -418,19 +450,30 @@ private function validate_amp_keyframe( $style ) {
 	 * @param DOMElement $element Node.
 	 */
 	private function collect_inline_styles( $element ) {
-		$style = $element->getAttribute( 'style' );
-		if ( ! $style ) {
+		$value = $element->getAttribute( 'style' );
+		if ( ! $value ) {
 			return;
 		}
 		$class = $element->getAttribute( 'class' );
 
-		$style = $this->process_style( $style );
-		if ( ! empty( $style ) ) {
-			$class_name = $this->generate_class_name( $style );
+		$properties = $this->process_style( $value );
+
+		if ( ! empty( $properties ) ) {
+			$class_name = $this->generate_class_name( $properties );
 			$new_class  = trim( $class . ' ' . $class_name );
 
+			$selector = '.' . $class_name;
+			$length   = strlen( sprintf( '%s { %s }', $selector, join( '; ', $properties ) . ';' ) );
+
+			if ( $this->current_custom_size + $length > $this->custom_max_size ) {
+				$this->remove_invalid_attribute( $element, 'style', array(
+					'message' => __( 'Too much CSS.', 'amp' ),
+				) );
+				return;
+			}
+
 			$element->setAttribute( 'class', $new_class );
-			$this->styles[ '.' . $class_name ] = $style;
+			$this->styles[ $selector ] = $properties;
 		}
 		$element->removeAttribute( 'style' );
 	}
@@ -440,26 +483,20 @@ private function collect_inline_styles( $element ) {
 	 *
 	 * @since 0.4
 	 *
-	 * @param string $string Style string.
-	 * @return array
+	 * @param string $css Style string.
+	 * @return array Style properties.
 	 */
-	private function process_style( $string ) {
-
-		/**
-		 * Filter properties
-		 */
-		$string = safecss_filter_attr( esc_html( $string ) );
+	private function process_style( $css ) {
 
-		if ( ! $string ) {
-			return array();
-		}
+		// Normalize whitespace.
+		$css = str_replace( array( "\n", "\r", "\t" ), '', $css );
 
 		/*
-		 * safecss returns a string but we want individual rules.
 		 * Use preg_split to break up rules by `;` but only if the
 		 * semi-colon is not inside parens (like a data-encoded image).
 		 */
-		$styles = array_map( 'trim', preg_split( '/;(?![^(]*\))/', $string ) );
+		$styles = preg_split( '/\s*;\s*(?![^(]*\))/', trim( $css, '; ' ) );
+		$styles = array_filter( $styles );
 
 		// Normalize the order of the styles.
 		sort( $styles );
@@ -468,12 +505,12 @@ private function process_style( $string ) {
 
 		// Normalize whitespace and filter rules.
 		foreach ( $styles as $index => $rule ) {
-			$arr2 = array_map( 'trim', explode( ':', $rule, 2 ) );
-			if ( 2 !== count( $arr2 ) ) {
+			$tuple = preg_split( '/\s*:\s*/', $rule, 2 );
+			if ( 2 !== count( $tuple ) ) {
 				continue;
 			}
 
-			list( $property, $value ) = $this->filter_style( $arr2[0], $arr2[1] );
+			list( $property, $value ) = $this->filter_style( $tuple[0], $tuple[1] );
 			if ( empty( $property ) || empty( $value ) ) {
 				continue;
 			}
@@ -498,14 +535,13 @@ private function process_style( $string ) {
 	 * @return array
 	 */
 	private function filter_style( $property, $value ) {
-
-		/**
+		/*
 		 * Remove overflow if value is `auto` or `scroll`; not allowed in AMP
 		 *
 		 * @todo This removal needs to be reported.
 		 * @see https://www.ampproject.org/docs/reference/spec.html#properties
 		 */
-		if ( preg_match( '#^overflow#i', $property ) && preg_match( '#^(auto|scroll)$#i', $value ) ) {
+		if ( preg_match( '#^overflow(-[xy])?$#i', $property ) && preg_match( '#^(auto|scroll)$#i', $value ) ) {
 			return array( false, false );
 		}
 
@@ -513,7 +549,7 @@ private function filter_style( $property, $value ) {
 			$property = 'max-width';
 		}
 
-		/**
+		/*
 		 * Remove `!important`; not allowed in AMP
 		 *
 		 * @todo This removal needs to be reported.
diff --git a/includes/sanitizers/class-amp-tag-and-attribute-sanitizer.php b/includes/sanitizers/class-amp-tag-and-attribute-sanitizer.php
index b4c0faeee31..2f884c14b27 100644
--- a/includes/sanitizers/class-amp-tag-and-attribute-sanitizer.php
+++ b/includes/sanitizers/class-amp-tag-and-attribute-sanitizer.php
@@ -103,6 +103,65 @@ public function __construct( $dom, $args = array() ) {
 
 		parent::__construct( $dom, $args );
 
+		if ( ! empty( $this->args['allow_dirty_styles'] ) ) {
+
+			// Allow style attribute on all elements.
+			$this->args['amp_globally_allowed_attributes']['style'] = array();
+
+			// Allow style elements.
+			$this->args['amp_allowed_tags']['style'][] = array(
+				'attr_spec_list' => array(
+					'type' => array(
+						'value_casei' => 'text/css',
+					),
+				),
+				'cdata'          => array(),
+				'tag_spec'       => array(
+					'spec_name' => 'style for Customizer preview',
+				),
+			);
+
+			// Allow stylesheet links.
+			$this->args['amp_allowed_tags']['link'][] = array(
+				'attr_spec_list' => array(
+					'async'       => array(),
+					'crossorigin' => array(),
+					'href'        => array(
+						'mandatory' => true,
+					),
+					'integrity'   => array(),
+					'media'       => array(),
+					'rel'         => array(
+						'dispatch_key' => 2,
+						'mandatory'    => true,
+						'value_casei'  => 'stylesheet',
+					),
+					'type'        => array(
+						'value_casei' => 'text/css',
+					),
+				),
+				'tag_spec'       => array(
+					'spec_name' => 'link rel=stylesheet for Customizer preview', // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedStylesheet
+				),
+			);
+		}
+
+		// Allow scripts if requested.
+		if ( ! empty( $this->args['allow_dirty_scripts'] ) ) {
+			$this->args['amp_allowed_tags']['script'][] = array(
+				'attr_spec_list' => array(
+					'type'  => array(),
+					'src'   => array(),
+					'async' => array(),
+					'defer' => array(),
+				),
+				'cdata'          => array(),
+				'tag_spec'       => array(
+					'spec_name' => 'scripts for Customizer preview',
+				),
+			);
+		}
+
 		// Prepare whitelists.
 		$this->allowed_tags = $this->args['amp_allowed_tags'];
 		foreach ( AMP_Rule_Spec::$additional_allowed_tags as $tag_name => $tag_rule_spec ) {
@@ -134,21 +193,15 @@ public function __construct( $dom, $args = array() ) {
 	 * Javascript URLs from https://cdn.ampproject.org
 	 *
 	 * @since 0.7
+	 * @see amp_register_default_scripts()
 	 *
-	 * @return string[] Returns component name as array key and JavaScript URL as array value,
-	 *                  respectively. Will return an empty array if sanitization has yet to be run
+	 * @return array() Returns component name as array key and true as value (or JavaScript URL string),
+	 *                  respectively. When true then the default component script URL will be used.
+	 *                  Will return an empty array if sanitization has yet to be run
 	 *                  or if it did not find any HTML elements to convert to AMP equivalents.
 	 */
 	public function get_scripts() {
-		$scripts = array();
-		foreach ( $this->script_components as $component ) {
-			$scripts[ $component ] = sprintf(
-				'https://cdn.ampproject.org/v0/%s-%s.js',
-				$component,
-				'latest'
-			);
-		}
-		return $scripts;
+		return array_fill_keys( $this->script_components, true );
 	}
 
 	/**
@@ -255,6 +308,27 @@ private function process_node( $node ) {
 		}
 		foreach ( $rule_spec_list as $id => $rule_spec ) {
 			if ( $this->validate_tag_spec_for_node( $node, $rule_spec[ AMP_Rule_Spec::TAG_SPEC ] ) ) {
+
+				// Expand extension_spec into a set of attr_spec_list.
+				if ( isset( $rule_spec[ AMP_Rule_Spec::TAG_SPEC ]['extension_spec'] ) ) {
+					$extension_spec = $rule_spec[ AMP_Rule_Spec::TAG_SPEC ]['extension_spec'];
+					$custom_attr    = 'amp-mustache' === $extension_spec['name'] ? 'custom-template' : 'custom-element';
+
+					$rule_spec[ AMP_Rule_Spec::ATTR_SPEC_LIST ][ $custom_attr ] = array(
+						AMP_Rule_Spec::VALUE     => $extension_spec['name'],
+						AMP_Rule_Spec::MANDATORY => true,
+					);
+
+					$rule_spec[ AMP_Rule_Spec::ATTR_SPEC_LIST ]['src'] = array(
+						AMP_Rule_Spec::VALUE_REGEX => implode( '', array(
+							'^',
+							preg_quote( 'https://cdn.ampproject.org/v0/' . $extension_spec['name'] . '-' ),
+							'(' . implode( '|', $extension_spec['allowed_versions'] ) . ')',
+							'\.js$',
+						) ),
+					);
+				}
+
 				$rule_spec_list_to_validate[ $id ] = $rule_spec;
 			}
 		}
@@ -359,11 +433,22 @@ private function process_node( $node ) {
 			$attr_spec_list
 		);
 
-		// Remove any remaining disallowed attributes.
-		$this->sanitize_disallowed_attributes_in_node( $node, $merged_attr_spec_list );
+		// Identify any remaining disallowed attributes.
+		$disallowed_attributes = $this->get_disallowed_attributes_in_node( $node, $merged_attr_spec_list );
+
+		// Identify attribute values that don't conform to the attr_spec.
+		$disallowed_attributes = $this->sanitize_disallowed_attribute_values_in_node( $node, $merged_attr_spec_list, $disallowed_attributes );
 
-		// Remove values that don't conform to the attr_spec.
-		$this->sanitize_disallowed_attribute_values_in_node( $node, $merged_attr_spec_list );
+		// If $disallowed_attributes is false then the entire element should be removed.
+		if ( false === $disallowed_attributes ) {
+			$this->remove_node( $node );
+			return;
+		}
+
+		// Remove all invalid attributes.
+		foreach ( $disallowed_attributes as $disallowed_attribute ) {
+			$this->remove_invalid_attribute( $node, $disallowed_attribute );
+		}
 
 		// Add required AMP component scripts if the element is still in the document.
 		if ( $node->parentNode ) {
@@ -460,12 +545,12 @@ private function validate_cdata_for_node( $element, $cdata_spec ) {
 	 */
 	private function validate_tag_spec_for_node( $node, $tag_spec ) {
 
-		// Always skip extension spec scripts since we manage the injection of these ourselves.
-		if ( isset( $tag_spec['extension_spec'] ) ) {
+		if ( ! empty( $tag_spec[ AMP_Rule_Spec::MANDATORY_PARENT ] ) && ! $this->has_parent( $node, $tag_spec[ AMP_Rule_Spec::MANDATORY_PARENT ] ) ) {
 			return false;
 		}
 
-		if ( ! empty( $tag_spec[ AMP_Rule_Spec::MANDATORY_PARENT ] ) && ! $this->has_parent( $node, $tag_spec[ AMP_Rule_Spec::MANDATORY_PARENT ] ) ) {
+		// Extension scripts must be in the head.
+		if ( isset( $tag_spec['extension_spec'] ) && ! $this->has_parent( $node, 'head' ) ) {
 			return false;
 		}
 
@@ -510,6 +595,14 @@ private function validate_attr_spec_list_for_node( $node, $attr_spec_list ) {
 			return 0.5;
 		}
 
+		if ( ! $node instanceof DOMElement ) {
+			/*
+			 * A DOMNode is not valid for checks so might
+			 * as well bail here is not an DOMElement.
+			 */
+			return 0;
+		}
+
 		foreach ( $node->attributes as $attr_name => $attr_node ) {
 			if ( ! isset( $attr_spec_list[ $attr_name ][ AMP_Rule_Spec::ALTERNATIVE_NAMES ] ) ) {
 				continue;
@@ -519,14 +612,6 @@ private function validate_attr_spec_list_for_node( $node, $attr_spec_list ) {
 			}
 		}
 
-		if ( ! $node instanceof DOMElement ) {
-			/*
-			 * A DOMNode is not valid for checks so might
-			 * as well bail here is not an DOMElement.
-			 */
-			return 0;
-		}
-
 		$score = 0;
 
 		/*
@@ -629,6 +714,19 @@ private function validate_attr_spec_list_for_node( $node, $attr_spec_list ) {
 				}
 			}
 
+			/*
+			 * If given attribute's value is a URL with a host, the host must
+			 * be valid
+			 */
+			if ( isset( $attr_spec_rule[ AMP_Rule_Spec::VALUE_URL ] ) ) {
+				$result = $this->check_attr_spec_rule_valid_url( $node, $attr_name, $attr_spec_rule );
+				if ( AMP_Rule_Spec::PASS === $result ) {
+					$score++;
+				} elseif ( AMP_Rule_Spec::FAIL === $result ) {
+					return 0;
+				}
+			}
+
 			/*
 			 * If the given attribute's value is *not* a relative path, and the rule's
 			 * value is `false`, then pass.
@@ -705,15 +803,16 @@ private function validate_attr_spec_list_for_node( $node, $attr_spec_list ) {
 	 *
 	 * @param DOMNode $node           Node.
 	 * @param array[] $attr_spec_list Attribute spec list.
+	 * @return DOMAttr[] Attributes to remove.
 	 */
-	private function sanitize_disallowed_attributes_in_node( $node, $attr_spec_list ) {
+	private function get_disallowed_attributes_in_node( $node, $attr_spec_list ) {
 
 		if ( ! $node instanceof DOMElement ) {
 			/**
 			 * If $node is only a DOMNode and not a DOMElement we can't
 			 * remove an attribute from it anyway.  So bail out now.
 			 */
-			return;
+			return array();
 		}
 
 		/*
@@ -728,12 +827,7 @@ private function sanitize_disallowed_attributes_in_node( $node, $attr_spec_list
 			}
 		}
 
-		foreach ( $attrs_to_remove as $attr ) {
-			$node->removeAttributeNode( $attr );
-			if ( isset( $this->args['remove_invalid_callback'], $attr->name ) ) {
-				call_user_func( $this->args['remove_invalid_callback'], $node, AMP_Validation_Utils::ATTRIBUTE_REMOVED, $attr->name );
-			}
-		}
+		return $attrs_to_remove;
 	}
 
 	/**
@@ -741,23 +835,29 @@ private function sanitize_disallowed_attributes_in_node( $node, $attr_spec_list
 	 *
 	 * Allowed values are found $this->globally_allowed_attributes and in parameter $attr_spec_list
 	 *
-	 * @param DOMNode   $node           Node.
-	 * @param array[][] $attr_spec_list Attribute spec list.
+	 * @param DOMNode   $node                       Node.
+	 * @param array[][] $attr_spec_list             Attribute spec list.
+	 * @param DOMAttr[] $attributes_pending_removal Attributes pending removal.
+	 * @return DOMAttr[]|false Attributes to remove, or false if the element itself should be removed.
 	 */
-	private function sanitize_disallowed_attribute_values_in_node( $node, $attr_spec_list ) {
+	private function sanitize_disallowed_attribute_values_in_node( $node, $attr_spec_list, $attributes_pending_removal ) {
 
 		if ( ! $node instanceof DOMElement ) {
 			/*
 			 * If $node is only a DOMNode and not a DOMElement we can't
 			 * remove an attribute from it anyway.  So bail out now.
 			 */
-			return;
+			return $attributes_pending_removal;
 		}
 
-		$this->delegated_sanitize_disallowed_attribute_values_in_node( $node, array_merge(
-			$this->globally_allowed_attributes,
-			$attr_spec_list
-		) );
+		return $this->delegated_sanitize_disallowed_attribute_values_in_node(
+			$node,
+			array_merge(
+				$this->globally_allowed_attributes,
+				$attr_spec_list
+			),
+			$attributes_pending_removal
+		);
 	}
 
 	/**
@@ -765,10 +865,12 @@ private function sanitize_disallowed_attribute_values_in_node( $node, $attr_spec
 	 *
 	 * @see $this->sanitize_disallowed_attribute_values_in_node() which delegates to this method
 	 *
-	 * @param DOMElement $node           Node.
-	 * @param array[][]  $attr_spec_list Attribute spec list.
+	 * @param DOMElement $node                       Node.
+	 * @param array[][]  $attr_spec_list             Attribute spec list.
+	 * @param DOMAttr[]  $attributes_pending_removal Attributes pending removal.
+	 * @return DOMAttr[]|false Attributes to remove, or false if the element itself should be removed.
 	 */
-	private function delegated_sanitize_disallowed_attribute_values_in_node( $node, $attr_spec_list ) {
+	private function delegated_sanitize_disallowed_attribute_values_in_node( $node, $attr_spec_list, $attributes_pending_removal ) {
 		$attrs_to_remove = array();
 
 		foreach ( $attr_spec_list as $attr_name => $attr_val ) {
@@ -781,7 +883,7 @@ private function delegated_sanitize_disallowed_attribute_values_in_node( $node,
 
 		foreach ( $node->attributes as $attr_name => $attr_node ) {
 
-			if ( ! isset( $attr_spec_list[ $attr_name ] ) ) {
+			if ( ! isset( $attr_spec_list[ $attr_name ] ) || in_array( $attr_node, $attributes_pending_removal, true ) ) {
 				continue;
 			}
 
@@ -803,6 +905,9 @@ private function delegated_sanitize_disallowed_attribute_values_in_node( $node,
 			} elseif ( isset( $attr_spec_rule[ AMP_Rule_Spec::VALUE_URL ][ AMP_Rule_Spec::ALLOWED_PROTOCOL ] ) &&
 				AMP_Rule_Spec::FAIL === $this->check_attr_spec_rule_allowed_protocol( $node, $attr_name, $attr_spec_rule ) ) {
 				$should_remove_node = true;
+			} elseif ( isset( $attr_spec_rule[ AMP_Rule_Spec::VALUE_URL ] ) &&
+				AMP_Rule_Spec::FAIL === $this->check_attr_spec_rule_valid_url( $node, $attr_name, $attr_spec_rule ) ) {
+				$should_remove_node = true;
 			} elseif ( isset( $attr_spec_rule[ AMP_Rule_Spec::VALUE_URL ][ AMP_Rule_Spec::ALLOW_RELATIVE ] ) &&
 				AMP_Rule_Spec::FAIL === $this->check_attr_spec_rule_disallowed_relative( $node, $attr_name, $attr_spec_rule ) ) {
 				$should_remove_node = true;
@@ -825,22 +930,24 @@ private function delegated_sanitize_disallowed_attribute_values_in_node( $node,
 
 				if ( $is_mandatory ) {
 					$this->remove_node( $node );
-					return;
+					return false;
 				}
 
-				$attrs_to_remove[] = $attr_name;
+				$attrs_to_remove[] = $attr_node;
 			}
 		}
 
 		// Remove the disallowed values.
-		foreach ( $attrs_to_remove as $attr_name ) {
-			if ( isset( $attr_spec_list[ $attr_name ][ AMP_Rule_Spec::VALUE_URL ][ AMP_Rule_Spec::ALLOW_EMPTY ] ) &&
-				( true === $attr_spec_list[ $attr_name ][ AMP_Rule_Spec::VALUE_URL ][ AMP_Rule_Spec::ALLOW_EMPTY ] ) ) {
-				$node->setAttribute( $attr_name, '' );
+		foreach ( $attrs_to_remove as $attr_node ) {
+			if ( isset( $attr_spec_list[ $attr_node->nodeName ][ AMP_Rule_Spec::VALUE_URL ][ AMP_Rule_Spec::ALLOW_EMPTY ] ) &&
+				( true === $attr_spec_list[ $attr_node->nodeName ][ AMP_Rule_Spec::VALUE_URL ][ AMP_Rule_Spec::ALLOW_EMPTY ] ) ) {
+				$attr_node->nodeValue = '';
 			} else {
-				$this->remove_invalid_attribute( $node, $attr_name );
+				$attributes_pending_removal[] = $attr_node;
 			}
 		}
+
+		return $attributes_pending_removal;
 	}
 
 	/**
@@ -1046,6 +1153,47 @@ private function check_attr_spec_rule_value_regex_casei( $node, $attr_name, $att
 		return AMP_Rule_Spec::NOT_APPLICABLE;
 	}
 
+	/**
+	 * Check if attribute has a valid host value
+	 *
+	 * @since 0.7
+	 *
+	 * @param DOMElement       $node           Node.
+	 * @param string           $attr_name      Attribute name.
+	 * @param array[]|string[] $attr_spec_rule Attribute spec rule.
+	 *
+	 * @return string:
+	 *      - AMP_Rule_Spec::PASS - $attr_name has a value that matches the rule.
+	 *      - AMP_Rule_Spec::FAIL - $attr_name has a value that does *not* match rule.
+	 *      - AMP_Rule_Spec::NOT_APPLICABLE - $attr_name does not exist or there
+	 *                                        is no rule for this attribute.
+	 */
+	private function check_attr_spec_rule_valid_url( $node, $attr_name, $attr_spec_rule ) {
+		if ( isset( $attr_spec_rule[ AMP_Rule_Spec::VALUE_URL ] ) ) {
+			if ( $node->hasAttribute( $attr_name ) ) {
+				$urls_to_test = preg_split( '/\s*,\s*/', $node->getAttribute( $attr_name ) );
+				foreach ( $urls_to_test as $url ) {
+					$url = urldecode( $url );
+					// Check if the host contains invalid chars.
+					$url_host = wp_parse_url( $url, PHP_URL_HOST );
+					if ( $url_host && preg_match( '/[!"#$%&\'()*+,\/:;<=>?@[\]^`{|}~\s]/i', $url_host ) ) {
+						return AMP_Rule_Spec::FAIL;
+					}
+
+					// Check if the protocol contains invalid chars.
+					$dots_pos = strpos( $url, ':' );
+					if ( false !== $dots_pos && preg_match( '/[!"#$%&\'()*+,\/:;<=>?@[\]^`{|}~\s]/i', substr( $url, 0, $dots_pos ) ) ) {
+						return AMP_Rule_Spec::FAIL;
+					}
+				}
+
+				return AMP_Rule_Spec::PASS;
+			}
+		}
+
+		return AMP_Rule_Spec::NOT_APPLICABLE;
+	}
+
 	/**
 	 * Check if attribute has a protocol value rule determine if it matches.
 	 *
@@ -1062,9 +1210,7 @@ private function check_attr_spec_rule_value_regex_casei( $node, $attr_name, $att
 	private function check_attr_spec_rule_allowed_protocol( $node, $attr_name, $attr_spec_rule ) {
 		if ( isset( $attr_spec_rule[ AMP_Rule_Spec::VALUE_URL ][ AMP_Rule_Spec::ALLOWED_PROTOCOL ] ) ) {
 			if ( $node->hasAttribute( $attr_name ) ) {
-				$attr_value   = $node->getAttribute( $attr_name );
-				$attr_value   = preg_replace( '/\s*,\s*/', ',', $attr_value );
-				$urls_to_test = explode( ',', $attr_value );
+				$urls_to_test = preg_split( '/\s*,\s*/', $node->getAttribute( $attr_name ) );
 				foreach ( $urls_to_test as $url ) {
 					/*
 					 * This seems to be an acceptable check since the AMP validator
@@ -1081,9 +1227,7 @@ private function check_attr_spec_rule_allowed_protocol( $node, $attr_name, $attr
 			} elseif ( isset( $attr_spec_rule[ AMP_Rule_Spec::ALTERNATIVE_NAMES ] ) ) {
 				foreach ( $attr_spec_rule[ AMP_Rule_Spec::ALTERNATIVE_NAMES ] as $alternative_name ) {
 					if ( $node->hasAttribute( $alternative_name ) ) {
-						$attr_value   = $node->getAttribute( $alternative_name );
-						$attr_value   = preg_replace( '/\s*,\s*/', ',', $attr_value );
-						$urls_to_test = explode( ',', $attr_value );
+						$urls_to_test = preg_split( '/\s*,\s*/', $node->getAttribute( $alternative_name ) );
 						foreach ( $urls_to_test as $url ) {
 							/*
 							 * This seems to be an acceptable check since the AMP validator
@@ -1120,9 +1264,7 @@ private function check_attr_spec_rule_allowed_protocol( $node, $attr_name, $attr
 	private function check_attr_spec_rule_disallowed_relative( $node, $attr_name, $attr_spec_rule ) {
 		if ( isset( $attr_spec_rule[ AMP_Rule_Spec::VALUE_URL ][ AMP_Rule_Spec::ALLOW_RELATIVE ] ) && ! ( $attr_spec_rule[ AMP_Rule_Spec::VALUE_URL ][ AMP_Rule_Spec::ALLOW_RELATIVE ] ) ) {
 			if ( $node->hasAttribute( $attr_name ) ) {
-				$attr_value   = $node->getAttribute( $attr_name );
-				$attr_value   = preg_replace( '/\s*,\s*/', ',', $attr_value );
-				$urls_to_test = explode( ',', $attr_value );
+				$urls_to_test = preg_split( '/\s*,\s*/', $node->getAttribute( $attr_name ) );
 				foreach ( $urls_to_test as $url ) {
 					$parsed_url = AMP_WP_Utils::parse_url( $url );
 
@@ -1141,9 +1283,7 @@ private function check_attr_spec_rule_disallowed_relative( $node, $attr_name, $a
 			} elseif ( isset( $attr_spec_rule[ AMP_Rule_Spec::ALTERNATIVE_NAMES ] ) ) {
 				foreach ( $attr_spec_rule[ AMP_Rule_Spec::ALTERNATIVE_NAMES ] as $alternative_name ) {
 					if ( $node->hasAttribute( $alternative_name ) ) {
-						$attr_value   = $node->getAttribute( $alternative_name );
-						$attr_value   = preg_replace( '/\s*,\s*/', ',', $attr_value );
-						$urls_to_test = explode( ',', $attr_value );
+						$urls_to_test = preg_split( '/\s*,\s*/', $node->getAttribute( $alternative_name ) );
 						foreach ( $urls_to_test as $url ) {
 							$parsed_url = AMP_WP_Utils::parse_url( $url );
 							if ( empty( $parsed_url['scheme'] ) ) {
@@ -1483,9 +1623,8 @@ private function remove_node( $node ) {
 			$node   = $parent;
 			$parent = $parent->parentNode;
 			if ( $parent ) {
-				$this->remove_invalid_child( $node );
+				$parent->removeChild( $node );
 			}
 		}
 	}
 }
-
diff --git a/includes/sanitizers/class-amp-video-sanitizer.php b/includes/sanitizers/class-amp-video-sanitizer.php
index 1dadfcc00eb..0512da17754 100644
--- a/includes/sanitizers/class-amp-video-sanitizer.php
+++ b/includes/sanitizers/class-amp-video-sanitizer.php
@@ -49,9 +49,10 @@ public function sanitize() {
 			$old_attributes = AMP_DOM_Utils::get_node_attributes_as_assoc_array( $node );
 
 			$new_attributes = $this->filter_attributes( $old_attributes );
-
-			$new_attributes = $this->enforce_fixed_height( $new_attributes );
-			$new_attributes = $this->enforce_sizes_attribute( $new_attributes );
+			$new_attributes = $this->set_layout( $new_attributes );
+			if ( empty( $new_attributes['layout'] ) && ! empty( $new_attributes['width'] ) && ! empty( $new_attributes['height'] ) ) {
+				$new_attributes['layout'] = 'responsive';
+			}
 
 			$new_node = AMP_DOM_Utils::create_node( $this->dom, 'amp-video', $new_attributes );
 
@@ -124,8 +125,7 @@ public function sanitize() {
 	 * @return array Returns HTML attributes; removes any not specifically declared above from input.
 	 */
 	private function filter_attributes( $attributes ) {
-		$out          = array();
-		$out['style'] = 'max-width:100%'; // Note that this will get moved to amp-custom style by AMP_Style_Sanitizer.
+		$out = array();
 
 		foreach ( $attributes as $name => $value ) {
 			switch ( $name ) {
diff --git a/includes/templates/class-amp-post-template.php b/includes/templates/class-amp-post-template.php
index a917e7aaf10..e7f420f0b77 100644
--- a/includes/templates/class-amp-post-template.php
+++ b/includes/templates/class-amp-post-template.php
@@ -349,7 +349,7 @@ private function build_post_featured_image() {
 
 		list( $sanitized_html, $featured_scripts, $featured_styles ) = AMP_Content_Sanitizer::sanitize(
 			$featured_html,
-			array( 'AMP_Img_Sanitizer' => array() ),
+			amp_get_content_sanitizers( $this->post ),
 			array(
 				'content_max_width' => $this->get( 'content_max_width' ),
 			)
diff --git a/includes/utils/class-amp-dom-utils.php b/includes/utils/class-amp-dom-utils.php
index 5288c044f2f..4a08dce4eb1 100644
--- a/includes/utils/class-amp-dom-utils.php
+++ b/includes/utils/class-amp-dom-utils.php
@@ -90,13 +90,15 @@ public static function get_dom( $document ) {
 			$document
 		);
 
-		/*
-		 * Replace noscript elements with placeholders since libxml<2.8 can parse them incorrectly.
-		 * When appearing in the head element, a noscript can cause the head to close prematurely
-		 * and the noscript gets moved to the body and anything after it which was in the head.
-		 * See <https://stackoverflow.com/questions/39013102/why-does-noscript-move-into-body-tag-instead-of-head-tag>.
-		 */
+		// Deal with bugs in older versions of libxml.
+		$added_back_compat_meta_content_type = false;
 		if ( version_compare( LIBXML_DOTTED_VERSION, '2.8', '<' ) ) {
+			/*
+			 * Replace noscript elements with placeholders since libxml<2.8 can parse them incorrectly.
+			 * When appearing in the head element, a noscript can cause the head to close prematurely
+			 * and the noscript gets moved to the body and anything after it which was in the head.
+			 * See <https://stackoverflow.com/questions/39013102/why-does-noscript-move-into-body-tag-instead-of-head-tag>.
+			 */
 			$document = preg_replace_callback(
 				'#<noscript[^>]*>.*?</noscript>#si',
 				function( $matches ) {
@@ -106,6 +108,21 @@ function( $matches ) {
 				},
 				$document
 			);
+
+			/*
+			 * Add a pre-HTML5-style declaration of the encoding since libxml<2.8 doesn't recognize
+			 * HTML5's meta charset. See <https://bugzilla.gnome.org/show_bug.cgi?id=655218>.
+			 */
+			$document = preg_replace(
+				'#(?=<meta\s+charset=["\']?([a-z0-9_-]+))#i',
+				'<meta http-equiv="Content-Type" content="text/html; charset=$1" id="meta-http-equiv-content-type">',
+				$document,
+				1,
+				$count
+			);
+			if ( 1 === $count ) {
+				$added_back_compat_meta_content_type = true;
+			}
 		}
 
 		/*
@@ -123,6 +140,14 @@ function( $matches ) {
 			return false;
 		}
 
+		// Remove pre-HTML5-style encoding declaration if added above.
+		if ( $added_back_compat_meta_content_type ) {
+			$meta_http_equiv_element = $dom->getElementById( 'meta-http-equiv-content-type' );
+			if ( $meta_http_equiv_element ) {
+				$meta_http_equiv_element->parentNode->removeChild( $meta_http_equiv_element );
+			}
+		}
+
 		return $dom;
 	}
 
@@ -231,14 +256,23 @@ public static function convert_amp_bind_attributes( $html ) {
 			return '<' . $tag_matches['name'] . $new_attrs . '>';
 		};
 
-		$html = preg_replace_callback(
+		$converted = preg_replace_callback(
 			// Match all start tags that probably contain a binding attribute.
-			'#<(?P<name>[a-zA-Z0-9_\-]+)(?P<attrs>\s+[^>]+\]=[^>]+)\s*>#',
+			'#<(?P<name>[a-zA-Z0-9_\-]+)(?P<attrs>\s[^>]+\]=[^>]+)>#',
 			$replace_callback,
 			$html
 		);
 
-		return $html;
+		/**
+		 * If the regex engine incurred an error during processing, for example exceeding the backtrack
+		 * limit, $converted will be null. In this case we return the originally passed document to allow
+		 * DOMDocument to attempt to load it.  If the AMP HTML doesn't make use of amp-bind or similar
+		 * attributes, then everything should still work.
+		 *
+		 * See https://github.com/Automattic/amp-wp/issues/993 for additional context on this issue.
+		 * See http://php.net/manual/en/pcre.constants.php for additional info on PCRE errors.
+		 */
+		return ( ! is_null( $converted ) ) ? $converted : $html;
 	}
 
 	/**
diff --git a/includes/utils/class-amp-validation-utils.php b/includes/utils/class-amp-validation-utils.php
index c7450248f81..bec91a67969 100644
--- a/includes/utils/class-amp-validation-utils.php
+++ b/includes/utils/class-amp-validation-utils.php
@@ -13,166 +13,379 @@
 class AMP_Validation_Utils {
 
 	/**
-	 * The argument if an attribute was removed.
+	 * Query var that triggers validation.
 	 *
-	 * @var array.
+	 * @var string
 	 */
-	const ATTRIBUTE_REMOVED = 'removed_attr';
+	const VALIDATE_QUERY_VAR = 'amp_validate';
 
 	/**
-	 * The argument if a node was removed.
+	 * Query var that enables validation debug mode, to disable removal of invalid elements/attributes.
 	 *
-	 * @var array.
+	 * @var string
 	 */
-	const NODE_REMOVED = 'removed';
+	const DEBUG_QUERY_VAR = 'amp_debug';
 
 	/**
-	 * Key for the markup value in the REST API endpoint.
+	 * Query var for cache-busting.
 	 *
-	 * @var string.
+	 * @var string
 	 */
-	const MARKUP_KEY = 'markup';
+	const CACHE_BUST_QUERY_VAR = 'amp_cache_bust';
 
 	/**
-	 * Key for the error value in the response.
+	 * The slug of the post type to store AMP errors.
 	 *
-	 * @var string.
+	 * @var string
 	 */
-	const ERROR_KEY = 'has_error';
+	const POST_TYPE_SLUG = 'amp_validation_error';
 
 	/**
-	 * Key of the AMP error query var.
+	 * The key in the response for the sources that have invalid output.
 	 *
-	 * @var string.
+	 * @var string
 	 */
-	const ERROR_QUERY_KEY = 'amp_error';
+	const SOURCES_INVALID_OUTPUT = 'sources_with_invalid_output';
 
 	/**
-	 * Query arg value if there is an AMP error in the post content.
+	 * Validation code for an invalid element.
 	 *
-	 * @var string.
+	 * @var string
 	 */
-	const ERROR_QUERY_VALUE = '1';
+	const INVALID_ELEMENT_CODE = 'invalid_element';
 
 	/**
-	 * Nonce name for the editor error message.
+	 * Validation code for an invalid attribute.
 	 *
-	 * @var string.
+	 * @var string
 	 */
-	const ERROR_NONCE = 'amp_nonce';
+	const INVALID_ATTRIBUTE_CODE = 'invalid_attribute';
 
 	/**
-	 * Nonce action for displaying the invalid AMP message.
+	 * Validation code for when script is enqueued (which is not allowed).
 	 *
-	 * @var string.
+	 * @var string
 	 */
-	const ERROR_NONCE_ACTION = 'invalid_amp_message';
+	const ENQUEUED_SCRIPT_CODE = 'enqueued_script';
 
 	/**
-	 * The attributes that the sanitizer removed.
+	 * The meta key for the AMP URL where the error occurred.
 	 *
-	 * @var array.
+	 * @var string
 	 */
-	public static $removed_attributes;
+	const AMP_URL_META = 'amp_url';
 
 	/**
-	 * The nodes that the sanitizer removed.
+	 * The key for removed elements.
 	 *
-	 * @var array.
+	 * @var string
 	 */
-	public static $removed_nodes;
+	const REMOVED_ELEMENTS = 'removed_elements';
+
+	/**
+	 * The key for removed attributes.
+	 *
+	 * @var string
+	 */
+	const REMOVED_ATTRIBUTES = 'removed_attributes';
+
+	/**
+	 * The key for removed sources.
+	 *
+	 * @var string
+	 */
+	const REMOVED_SOURCES = 'removed_sources';
+
+	/**
+	 * The action to recheck URLs for AMP validity.
+	 *
+	 * @var string
+	 */
+	const RECHECK_ACTION = 'amp_recheck';
+
+	/**
+	 * The query arg for whether there are remaining errors after rechecking URLs.
+	 *
+	 * @var string
+	 */
+	const REMAINING_ERRORS = 'amp_remaining_errors';
+
+	/**
+	 * The query arg for the number of URLs tested.
+	 *
+	 * @var string
+	 */
+	const URLS_TESTED = 'amp_urls_tested';
+
+	/**
+	 * The nonce action for rechecking a URL.
+	 *
+	 * @var string
+	 */
+	const NONCE_ACTION = 'amp_recheck_';
+
+	/**
+	 * HTTP response header name containing JSON-serialized validation errors.
+	 *
+	 * @var string
+	 */
+	const VALIDATION_ERRORS_RESPONSE_HEADER_NAME = 'X-AMP-Validation-Errors';
+
+	/**
+	 * Transient key to store validation errors when activating a plugin.
+	 *
+	 * @var string
+	 */
+	const PLUGIN_ACTIVATION_VALIDATION_ERRORS_TRANSIENT_KEY = 'amp_plugin_activation_validation_errors';
+
+	/**
+	 * The name of the side meta box on the CPT post.php page.
+	 *
+	 * @var string
+	 */
+	const STATUS_META_BOX = 'amp_validation_status';
+
+	/**
+	 * The name of the side meta box on the CPT post.php page.
+	 *
+	 * @var string
+	 */
+	const VALIDATION_ERRORS_META_BOX = 'amp_validation_errors';
+
+	/**
+	 * The errors encountered when validating.
+	 *
+	 * @var array[][] {
+	 *     @type string  $code        Error code.
+	 *     @type string  $node_name   Name of removed node.
+	 *     @type string  $parent_name Name of parent node.
+	 * }
+	 */
+	public static $validation_errors = array();
+
+	/**
+	 * Sources that enqueue each script.
+	 *
+	 * @var array
+	 */
+	public static $enqueued_script_sources = array();
+
+	/**
+	 * Sources that enqueue each style.
+	 *
+	 * @var array
+	 */
+	public static $enqueued_style_sources = array();
+
+	/**
+	 * Post IDs for posts that have been updated which need to be re-validated.
+	 *
+	 * @var int[]
+	 */
+	public static $posts_pending_frontend_validation = array();
+
+	/**
+	 * Current sources gathered for a given hook currently being run.
+	 *
+	 * @see AMP_Validation_Utils::wrap_hook_callbacks()
+	 * @see AMP_Validation_Utils::decorate_filter_source()
+	 * @var array[]
+	 */
+	protected static $current_hook_source_stack = array();
 
 	/**
 	 * Add the actions.
 	 *
-	 * @return void.
+	 * @return void
 	 */
 	public static function init() {
-		add_action( 'rest_api_init', array( __CLASS__, 'amp_rest_validation' ) );
-		add_action( 'save_post', array( __CLASS__, 'validate_content' ), 10, 2 );
-		add_action( 'edit_form_top', array( __CLASS__, 'display_error' ) );
+		if ( current_theme_supports( 'amp' ) ) {
+			add_action( 'init', array( __CLASS__, 'register_post_type' ) );
+			add_filter( 'dashboard_glance_items', array( __CLASS__, 'filter_dashboard_glance_items' ) );
+			add_action( 'rightnow_end', array( __CLASS__, 'print_dashboard_glance_styles' ) );
+			add_action( 'save_post', array( __CLASS__, 'handle_save_post_prompting_validation' ), 10, 2 );
+		}
+
+		add_action( 'edit_form_top', array( __CLASS__, 'print_edit_form_validation_status' ), 10, 2 );
+		add_action( 'all_admin_notices', array( __CLASS__, 'plugin_notice' ) );
+		add_filter( 'manage_' . self::POST_TYPE_SLUG . '_posts_columns', array( __CLASS__, 'add_post_columns' ) );
+		add_action( 'manage_posts_custom_column', array( __CLASS__, 'output_custom_column' ), 10, 2 );
+		add_filter( 'post_row_actions', array( __CLASS__, 'filter_row_actions' ), 10, 2 );
+		add_filter( 'bulk_actions-edit-' . self::POST_TYPE_SLUG, array( __CLASS__, 'add_bulk_action' ), 10, 2 );
+		add_filter( 'handle_bulk_actions-edit-' . self::POST_TYPE_SLUG, array( __CLASS__, 'handle_bulk_action' ), 10, 3 );
+		add_action( 'admin_notices', array( __CLASS__, 'remaining_error_notice' ) );
+		add_action( 'post_action_' . self::RECHECK_ACTION, array( __CLASS__, 'handle_inline_recheck' ) );
+		add_action( 'admin_menu', array( __CLASS__, 'remove_publish_meta_box' ) );
+		add_action( 'admin_menu', array( __CLASS__, 'add_admin_menu_validation_status_count' ) );
+		add_action( 'add_meta_boxes', array( __CLASS__, 'add_meta_boxes' ) );
+
+		// Actions and filters involved in validation.
+		add_action( 'activate_plugin', function() {
+			if ( ! has_action( 'shutdown', array( __CLASS__, 'validate_after_plugin_activation' ) ) ) {
+				add_action( 'shutdown', array( __CLASS__, 'validate_after_plugin_activation' ) ); // Shutdown so all plugins will have been activated.
+			}
+		} );
+	}
+
+	/**
+	 * Add count of how many validation error posts there are to the admin menu.
+	 */
+	public static function add_admin_menu_validation_status_count() {
+		global $submenu;
+		if ( ! isset( $submenu[ AMP_Options_Manager::OPTION_NAME ] ) ) {
+			return;
+		}
+		$count = wp_count_posts( self::POST_TYPE_SLUG );
+		if ( empty( $count->publish ) ) {
+			return;
+		}
+		foreach ( $submenu[ AMP_Options_Manager::OPTION_NAME ] as &$submenu_item ) {
+			if ( 'edit.php?post_type=' . self::POST_TYPE_SLUG === $submenu_item[2] ) {
+				$submenu_item[0] .= ' <span class="awaiting-mod"><span class="pending-count">' . esc_html( $count->publish ) . '</span></span>';
+				break;
+			}
+		}
 	}
 
 	/**
-	 * Tracks when a sanitizer removes an attribute or node.
+	 * Filter At a Glance items add AMP Validation Errors.
 	 *
-	 * @param DOMNode|DOMElement $node         The node in which there was a removal.
-	 * @param string             $removal_type The removal: 'removed_attr' for an attribute, or 'removed' for a node or element.
-	 * @param string             $attr_name    The name of the attribute removed (optional).
-	 * @return void.
+	 * @param array $items At a glance items.
+	 * @return array Items.
 	 */
-	public static function track_removed( $node, $removal_type, $attr_name = null ) {
-		if ( ( self::ATTRIBUTE_REMOVED === $removal_type ) && isset( $attr_name ) ) { // phpcs:ignore WordPress.NamingConventions.ValidVariableName.NotSnakeCaseMemberVar
-			self::$removed_attributes = self::increment_count( self::$removed_attributes, $attr_name );
-		} elseif ( ( self::NODE_REMOVED === $removal_type ) && isset( $node->nodeName ) ) {
-			self::$removed_nodes = self::increment_count( self::$removed_nodes, $node->nodeName ); // phpcs:ignore WordPress.NamingConventions.ValidVariableName.NotSnakeCaseMemberVar
+	public static function filter_dashboard_glance_items( $items ) {
+		$counts = wp_count_posts( self::POST_TYPE_SLUG );
+		if ( ! empty( $counts->publish ) ) {
+			$items[] = sprintf(
+				'<a class="amp-validation-errors" href="%s">%s</a>',
+				esc_url( admin_url( 'edit.php?post_type=' . self::POST_TYPE_SLUG ) ),
+				esc_html( sprintf(
+					/* translators: %s is the validation error count */
+					_n( '%s AMP Validation Error', '%s AMP Validation Errors', $counts->publish, 'amp' ),
+					$counts->publish
+				) )
+			);
 		}
+		return $items;
 	}
 
 	/**
-	 * Tracks when a sanitizer removes an attribute or node.
+	 * Print styles for the At a Glance widget.
+	 */
+	public static function print_dashboard_glance_styles() {
+		?>
+		<style>
+			#dashboard_right_now .amp-validation-errors {
+				color: #a00;
+			}
+			#dashboard_right_now .amp-validation-errors:before {
+				content: "\f534";
+			}
+			#dashboard_right_now .amp-validation-errors:hover {
+				color: #dc3232;
+				border: none;
+			}
+		</style>
+		<?php
+	}
+
+	/**
+	 * Add hooks for doing validation during preprocessing/sanitizing.
+	 */
+	public static function add_validation_hooks() {
+		self::wrap_widget_callbacks();
+
+		add_action( 'all', array( __CLASS__, 'wrap_hook_callbacks' ) );
+		$wrapped_filters = array( 'the_content', 'the_excerpt' );
+		foreach ( $wrapped_filters as $wrapped_filter ) {
+			add_filter( $wrapped_filter, array( __CLASS__, 'decorate_filter_source' ), PHP_INT_MAX );
+		}
+
+		add_filter( 'do_shortcode_tag', array( __CLASS__, 'decorate_shortcode_source' ), -1, 2 );
+		add_filter( 'amp_content_sanitizers', array( __CLASS__, 'add_validation_callback' ) );
+	}
+
+	/**
+	 * Handle save_post action to queue re-validation of the post on the frontend.
 	 *
-	 * @param array  $histogram The count of attributes or nodes removed.
-	 * @param string $key       The attribute or node name removed.
-	 * @return array $histogram The incremented histogram.
+	 * @see AMP_Validation_Utils::validate_queued_posts_on_frontend()
+	 * @param int     $post_id Post ID.
+	 * @param WP_Post $post    Post.
 	 */
-	public static function increment_count( $histogram, $key ) {
-		$current_value     = isset( $histogram[ $key ] ) ? $histogram[ $key ] : 0;
-		$histogram[ $key ] = $current_value + 1;
-		return $histogram;
+	public static function handle_save_post_prompting_validation( $post_id, $post ) {
+		$should_validate_post = (
+			is_post_type_viewable( $post->post_type )
+			&&
+			! wp_is_post_autosave( $post )
+			&&
+			! wp_is_post_revision( $post )
+		);
+		if ( $should_validate_post ) {
+			self::$posts_pending_frontend_validation[] = $post_id;
+
+			// The reason for shutdown is to ensure that all postmeta changes have been saved, including whether AMP is enabled.
+			if ( ! has_action( 'shutdown', array( __CLASS__, 'validate_queued_posts_on_frontend' ) ) ) {
+				add_action( 'shutdown', array( __CLASS__, 'validate_queued_posts_on_frontend' ) );
+			}
+		}
 	}
 
 	/**
-	 * Gets whether a node was removed in a sanitizer.
+	 * Validate the posts pending frontend validation.
 	 *
-	 * @return boolean.
+	 * @see AMP_Validation_Utils::handle_save_post_prompting_validation()
 	 */
-	public static function was_node_removed() {
-		return ! empty( self::$removed_nodes );
+	public static function validate_queued_posts_on_frontend() {
+		$posts = array_filter(
+			array_map( 'get_post', self::$posts_pending_frontend_validation ),
+			function( $post ) {
+				return $post && post_supports_amp( $post ) && 'trash' !== $post->post_status;
+			}
+		);
+
+		// @todo Only validate the first and then queue the rest in WP Cron?
+		foreach ( $posts as $post ) {
+			$url = amp_get_permalink( $post->ID );
+			if ( ! $url ) {
+				continue;
+			}
+
+			$validation_errors = self::validate_url( $url );
+			if ( is_wp_error( $validation_errors ) ) {
+				continue;
+			}
+
+			self::store_validation_errors( $validation_errors, $url );
+		}
 	}
 
 	/**
 	 * Processes markup, to determine AMP validity.
 	 *
 	 * Passes $markup through the AMP sanitizers.
-	 * Also passes a 'remove_invalid_callback' to keep track of stripped attributes and nodes.
+	 * Also passes a 'validation_error_callback' to keep track of stripped attributes and nodes.
 	 *
 	 * @param string $markup The markup to process.
-	 * @return void.
+	 * @return string Sanitized markup.
 	 */
 	public static function process_markup( $markup ) {
-		$args = array(
-			'content_max_width' => ! empty( $content_width ) ? $content_width : AMP_Post_Template::CONTENT_MAX_WIDTH,
+		AMP_Theme_Support::register_content_embed_handlers();
+
+		/** This filter is documented in wp-includes/post-template.php */
+		$markup = apply_filters( 'the_content', $markup );
+		$args   = array(
+			'content_max_width'         => ! empty( $content_width ) ? $content_width : AMP_Post_Template::CONTENT_MAX_WIDTH,
+			'validation_error_callback' => 'AMP_Validation_Utils::add_validation_error',
 		);
-		if ( self::is_authorized() ) {
-			$args['remove_invalid_callback'] = 'AMP_Validation_Utils::track_removed';
-		}
-		AMP_Content_Sanitizer::sanitize( $markup, amp_get_content_sanitizers(), $args );
-	}
 
-	/**
-	 * Registers the REST API endpoint for validation.
-	 *
-	 * @return void.
-	 */
-	public static function amp_rest_validation() {
-		register_rest_route( 'amp-wp/v1', '/validate', array(
-			'methods'             => 'POST',
-			'callback'            => array( __CLASS__, 'validate_markup' ),
-			'args'                => array(
-				self::MARKUP_KEY => array(
-					'validate_callback' => array( __CLASS__, 'validate_arg' ),
-				),
-			),
-			'permission_callback' => array( __CLASS__, 'has_cap' ),
-		) );
+		$results = AMP_Content_Sanitizer::sanitize( $markup, amp_get_content_sanitizers(), $args );
+		return $results[0];
 	}
 
 	/**
 	 * Whether the user has the required capability.
 	 *
 	 * Checks for permissions before validating.
-	 * Also serves as the permission callback for REST requests.
 	 *
 	 * @return boolean $has_cap Whether the current user has the capability.
 	 */
@@ -181,45 +394,114 @@ public static function has_cap() {
 	}
 
 	/**
-	 * Validate the markup passed to the REST API.
+	 * Add validation error.
+	 *
+	 * @param array $data {
+	 *     Data.
 	 *
-	 * @param WP_REST_Request $request The REST request.
-	 * @return array|WP_Error.
+	 *     @type string $code Error code.
+	 *     @type DOMElement|DOMNode $node The removed node.
+	 * }
 	 */
-	public static function validate_markup( WP_REST_Request $request ) {
-		$json = $request->get_json_params();
-		if ( empty( $json[ self::MARKUP_KEY ] ) ) {
-			return new WP_Error( 'no_markup', 'No markup passed to validator', array(
-				'status' => 404,
-			) );
+	public static function add_validation_error( array $data ) {
+		$node = null;
+
+		if ( isset( $data['node'] ) && $data['node'] instanceof DOMNode ) {
+			$node = $data['node'];
+			unset( $data['node'] );
+			$data['node_name'] = $node->nodeName;
+			$data['sources']   = self::locate_sources( $node );
+			if ( $node->parentNode ) {
+				$data['parent_name'] = $node->parentNode->nodeName;
+			}
 		}
 
-		return self::get_response( $json[ self::MARKUP_KEY ] );
+		if ( $node instanceof DOMElement ) {
+			if ( ! isset( $data['code'] ) ) {
+				$data['code'] = self::INVALID_ELEMENT_CODE;
+			}
+			$data['node_attributes'] = array();
+			foreach ( $node->attributes as $attribute ) {
+				$data['node_attributes'][ $attribute->nodeName ] = $attribute->nodeValue;
+			}
+
+			$is_enqueued_link = (
+				'link' === $node->nodeName
+				&&
+				preg_match( '/(?P<handle>.+)-css$/', (string) $node->getAttribute( 'id' ), $matches )
+				&&
+				isset( self::$enqueued_style_sources[ $matches['handle'] ] )
+			);
+			if ( $is_enqueued_link ) {
+				$data['sources'] = self::$enqueued_style_sources[ $matches['handle'] ];
+			}
+		} elseif ( $node instanceof DOMAttr ) {
+			if ( ! isset( $data['code'] ) ) {
+				$data['code'] = self::INVALID_ATTRIBUTE_CODE;
+			}
+			$data['element_attributes'] = array();
+			if ( $node->parentNode && $node->parentNode->hasAttributes() ) {
+				foreach ( $node->parentNode->attributes as $attribute ) {
+					$data['element_attributes'][ $attribute->nodeName ] = $attribute->nodeValue;
+				}
+			}
+		}
+
+		if ( ! isset( $data['code'] ) ) {
+			$data['code'] = 'unknown';
+		}
+
+		self::$validation_errors[] = $data;
 	}
 
 	/**
 	 * Gets the AMP validation response.
 	 *
-	 * If $markup isn't passed,
-	 * It will return the validation errors the sanitizers found in rendering the page.
+	 * Returns the current validation errors the sanitizers found in rendering the page.
 	 *
-	 * @param string $markup   To validate for AMP compatibility (optional).
-	 * @return array $response The AMP validity of the markup.
+	 * @param array $validation_errors Validation errors.
+	 * @return array The AMP validity of the markup.
 	 */
-	public static function get_response( $markup = null ) {
-		$response = array();
-		if ( isset( $markup ) ) {
-			self::process_markup( $markup );
-			$response['processed_markup'] = $markup;
+	public static function summarize_validation_errors( $validation_errors ) {
+		$results            = array();
+		$removed_elements   = array();
+		$removed_attributes = array();
+		$invalid_sources    = array();
+		foreach ( $validation_errors as $validation_error ) {
+			$code = isset( $validation_error['code'] ) ? $validation_error['code'] : null;
+
+			if ( self::INVALID_ELEMENT_CODE === $code ) {
+				if ( ! isset( $removed_elements[ $validation_error['node_name'] ] ) ) {
+					$removed_elements[ $validation_error['node_name'] ] = 0;
+				}
+				$removed_elements[ $validation_error['node_name'] ] += 1;
+			} elseif ( self::INVALID_ATTRIBUTE_CODE === $code ) {
+				if ( ! isset( $removed_attributes[ $validation_error['node_name'] ] ) ) {
+					$removed_attributes[ $validation_error['node_name'] ] = 0;
+				}
+				$removed_attributes[ $validation_error['node_name'] ] += 1;
+			}
+
+			if ( ! empty( $validation_error['sources'] ) ) {
+				$source = array_pop( $validation_error['sources'] );
+
+				if ( isset( $source['type'], $source['name'] ) ) {
+					$invalid_sources[ $source['type'] ][] = $source['name'];
+				}
+			}
 		}
-		$response = array_merge( array(
-			self::ERROR_KEY      => self::was_node_removed(),
-			'removed_nodes'      => self::$removed_nodes,
-			'removed_attributes' => self::$removed_attributes,
-		), $response );
-		self::reset_removed();
 
-		return $response;
+		$results = array_merge(
+			array(
+				self::SOURCES_INVALID_OUTPUT => $invalid_sources,
+			),
+			compact(
+				'removed_elements',
+				'removed_attributes'
+			),
+		$results );
+
+		return $results;
 	}
 
 	/**
@@ -229,127 +511,1284 @@ public static function get_response( $markup = null ) {
 	 * these static values will remain.
 	 * So reset them in case another test is needed.
 	 *
-	 * @return void.
+	 * @return void
 	 */
-	public static function reset_removed() {
-		self::$removed_nodes      = null;
-		self::$removed_attributes = null;
+	public static function reset_validation_results() {
+		self::$validation_errors       = array();
+		self::$enqueued_style_sources  = array();
+		self::$enqueued_script_sources = array();
 	}
 
 	/**
-	 * Validate the argument in the REST API request.
+	 * Checks the AMP validity of the post content.
 	 *
-	 * It would be ideal to simply pass 'is_string' in register_rest_route().
-	 * But it always returned false.
+	 * If it's not valid AMP, it displays an error message above the 'Classic' editor.
 	 *
-	 * @param mixed $arg      The argument to validate.
-	 * @return boolean $is_valid Whether the argument is valid.
+	 * @param WP_Post $post The updated post.
+	 * @return void
 	 */
-	public static function validate_arg( $arg ) {
-		return is_string( $arg );
+	public static function print_edit_form_validation_status( $post ) {
+		if ( ! post_supports_amp( $post ) || ! self::has_cap() ) {
+			return;
+		}
+
+		$url                    = null;
+		$validation_status_post = null;
+		$validation_errors      = array();
+
+		// Validate post content outside frontend context.
+		if ( post_type_supports( $post->post_type, 'editor' ) ) {
+			self::process_markup( $post->post_content );
+			$validation_errors = array_merge(
+				$validation_errors,
+				self::$validation_errors
+			);
+			self::reset_validation_results();
+		}
+
+		// Incorporate frontend validation status if there is a known URL for the post.
+		if ( is_post_type_viewable( $post->post_type ) ) {
+			$url = amp_get_permalink( $post->ID );
+
+			$validation_status_post = self::get_validation_status_post( $url );
+			if ( $validation_status_post ) {
+				$data = json_decode( $validation_status_post->post_content, true );
+				if ( is_array( $data ) ) {
+					$validation_errors = array_merge( $validation_errors, $data );
+				}
+			}
+		}
+
+		if ( empty( $validation_errors ) ) {
+			return;
+		}
+
+		echo '<div class="notice notice-warning">';
+		echo '<p>';
+		esc_html_e( 'Warning: There is content which fails AMP validation; it will be stripped when served as AMP.', 'amp' );
+		if ( $validation_status_post || $url ) {
+			if ( $validation_status_post ) {
+				echo sprintf(
+					' <a href="%s" target="_blank">%s</a>',
+					esc_url( get_edit_post_link( $validation_status_post ) ),
+					esc_html__( 'Details', 'amp' )
+				);
+			}
+			if ( $url ) {
+				if ( $validation_status_post ) {
+					echo ' | ';
+				}
+				echo sprintf(
+					' <a href="%s" aria-label="%s" target="_blank">%s</a>',
+					esc_url( self::get_debug_url( $url ) ),
+					esc_attr__( 'Validate URL on frontend but without invalid elements/attributes removed', 'amp' ),
+					esc_html__( 'Debug', 'amp' )
+				);
+			}
+		}
+		echo '</p>';
+
+		$results      = self::summarize_validation_errors( array_unique( $validation_errors, SORT_REGULAR ) );
+		$removed_sets = array();
+		if ( ! empty( $results[ self::REMOVED_ELEMENTS ] ) && is_array( $results[ self::REMOVED_ELEMENTS ] ) ) {
+			$removed_sets[] = array(
+				'label' => __( 'Invalid elements:', 'amp' ),
+				'names' => array_map( 'sanitize_key', $results[ self::REMOVED_ELEMENTS ] ),
+			);
+		}
+		if ( ! empty( $results[ self::REMOVED_ATTRIBUTES ] ) && is_array( $results[ self::REMOVED_ATTRIBUTES ] ) ) {
+			$removed_sets[] = array(
+				'label' => __( 'Invalid attributes:', 'amp' ),
+				'names' => array_map( 'sanitize_key', $results[ self::REMOVED_ATTRIBUTES ] ),
+			);
+		}
+		// @todo There are other kinds of errors other than REMOVED_ELEMENTS and REMOVED_ATTRIBUTES.
+		foreach ( $removed_sets as $removed_set ) {
+			printf( '<p>%s ', esc_html( $removed_set['label'] ) );
+			self::output_removed_set( $removed_set['names'] );
+			echo '</p>';
+		}
+
+		echo '</div>';
 	}
 
 	/**
-	 * On updating a post, this checks the AMP validity of the content.
+	 * Get source start comment.
 	 *
-	 * If it's not valid AMP, it adds a query arg to the redirect URL.
-	 * This will cause an error message to appear above the 'Classic' editor.
+	 * @param array $source   Source data.
+	 * @param bool  $is_start Whether the comment is the start or end.
+	 * @return string HTML Comment.
+	 */
+	public static function get_source_comment( array $source, $is_start = true ) {
+		unset( $source['reflection'] );
+		return sprintf(
+			'<!--%samp-source-stack %s-->',
+			$is_start ? '' : '/',
+			str_replace( '--', '', wp_json_encode( $source ) )
+		);
+	}
+
+	/**
+	 * Parse source comment.
 	 *
-	 * @param integer $post_id The ID of the updated post.
-	 * @param WP_Post $post    The updated post.
-	 * @return void.
+	 * @param DOMComment $comment Comment.
+	 * @return array|null Parsed source or null if not a source comment.
+	 */
+	public static function parse_source_comment( DOMComment $comment ) {
+		if ( ! preg_match( '#^\s*(?P<closing>/)?amp-source-stack\s+(?P<args>{.+})\s*$#s', $comment->nodeValue, $matches ) ) {
+			return null;
+		}
+
+		$source  = json_decode( $matches['args'], true );
+		$closing = ! empty( $matches['closing'] );
+
+		return compact( 'source', 'closing' );
+	}
+
+	/**
+	 * Walk back tree to find the open sources.
+	 *
+	 * @param DOMNode $node Node to look for.
+	 * @return array[][] {
+	 *       The data of the removed sources (theme, plugin, or mu-plugin).
+	 *
+	 *       @type string $name The name of the source.
+	 *       @type string $type The type of the source.
+	 * }
+	 */
+	public static function locate_sources( DOMNode $node ) {
+		$xpath    = new DOMXPath( $node->ownerDocument );
+		$comments = $xpath->query( 'preceding::comment()[ starts-with( ., "amp-source-stack" ) or starts-with( ., "/amp-source-stack" ) ]', $node );
+		$sources  = array();
+		foreach ( $comments as $comment ) {
+			$parsed_comment = self::parse_source_comment( $comment );
+			if ( ! $parsed_comment ) {
+				continue;
+			}
+			if ( $parsed_comment['closing'] ) {
+				array_pop( $sources );
+			} else {
+				$sources[] = $parsed_comment['source'];
+			}
+		}
+		return $sources;
+	}
+
+	/**
+	 * Remove source comments.
+	 *
+	 * @param DOMDocument $dom Document.
+	 */
+	public static function remove_source_comments( $dom ) {
+		$xpath    = new DOMXPath( $dom );
+		$comments = array();
+		foreach ( $xpath->query( '//comment()[ starts-with( ., "amp-source-stack" ) or starts-with( ., "/amp-source-stack" ) ]' ) as $comment ) {
+			if ( self::parse_source_comment( $comment ) ) {
+				$comments[] = $comment;
+			}
+		}
+		foreach ( $comments as $comment ) {
+			$comment->parentNode->removeChild( $comment );
+		}
+	}
+
+	/**
+	 * Wrap callbacks for registered widgets to keep track of queued assets and the source for anything printed for validation.
+	 *
+	 * @global array $wp_filter
+	 * @return void
 	 */
-	public static function validate_content( $post_id, $post ) {
-		unset( $post_id );
-		if ( ! post_supports_amp( $post ) || ! self::is_authorized() ) {
+	public static function wrap_widget_callbacks() {
+		global $wp_registered_widgets;
+		foreach ( $wp_registered_widgets as $widget_id => &$registered_widget ) {
+			$source = self::get_source( $registered_widget['callback'] );
+			if ( ! $source ) {
+				continue;
+			}
+			$source['widget_id'] = $widget_id;
+
+			$function      = $registered_widget['callback'];
+			$accepted_args = 2; // For the $instance and $args arguments.
+			$callback      = compact( 'function', 'accepted_args', 'source' );
+
+			$registered_widget['callback'] = self::wrapped_callback( $callback );
+		}
+	}
+
+	/**
+	 * Wrap filter/action callback functions for a given hook.
+	 *
+	 * Wrapped callback functions are reset to their original functions after invocation.
+	 * This runs at the 'all' action. The shutdown hook is excluded.
+	 *
+	 * @global WP_Hook[] $wp_filter
+	 * @param string $hook Hook name for action or filter.
+	 * @return void
+	 */
+	public static function wrap_hook_callbacks( $hook ) {
+		global $wp_filter;
+
+		if ( ! isset( $wp_filter[ $hook ] ) || 'shutdown' === $hook ) {
 			return;
 		}
-		/** This filter is documented in wp-includes/post-template.php */
-		$filtered_content = apply_filters( 'the_content', $post->post_content, $post->ID );
-		$response         = self::get_response( $filtered_content );
-		if ( isset( $response[ self::ERROR_KEY ] ) && ( true === $response[ self::ERROR_KEY ] ) ) {
-			add_filter( 'redirect_post_location', function( $location ) use ( $response ) {
-				$location = AMP_Validation_Utils::error_message( $location );
-				$location = add_query_arg(
-					array(
-						'removed_elements'   => array_keys( $response['removed_nodes'] ),
-						'removed_attributes' => array_keys( $response['removed_attributes'] ),
-					),
-					$location
-				);
-				return $location;
-			} );
+
+		self::$current_hook_source_stack[ $hook ] = array();
+		foreach ( $wp_filter[ $hook ]->callbacks as $priority => &$callbacks ) {
+			foreach ( $callbacks as &$callback ) {
+				$source = self::get_source( $callback['function'] );
+				if ( ! $source ) {
+					continue;
+				}
+
+				$reflection = $source['reflection'];
+				unset( $source['reflection'] ); // Omit from stored source.
+
+				// Add hook to stack for decorate_filter_source to read from.
+				self::$current_hook_source_stack[ $hook ][] = $source;
+
+				/*
+				 * A current limitation with wrapping callbacks is that the wrapped function cannot have
+				 * any parameters passed by reference. Without this the result is:
+				 *
+				 * > PHP Warning:  Parameter 1 to wp_default_styles() expected to be a reference, value given.
+				 */
+				if ( self::has_parameters_passed_by_reference( $reflection ) ) {
+					continue;
+				}
+
+				$source['hook']    = $hook;
+				$original_function = $callback['function'];
+				$wrapped_callback  = self::wrapped_callback( array_merge(
+					$callback,
+					compact( 'priority', 'source', 'hook' )
+				) );
+
+				$callback['function'] = function() use ( &$callback, $wrapped_callback, $original_function ) {
+					$callback['function'] = $original_function; // Restore original.
+					return call_user_func_array( $wrapped_callback, func_get_args() );
+				};
+			}
 		}
 	}
 
 	/**
-	 * Whether the current user is authorized.
+	 * Determine whether the given reflection method/function has params passed by reference.
 	 *
-	 * This checks that the user has a certain capability and the nonce is valid.
-	 * It will only return true when updating the post on:
-	 * wp-admin/post.php
-	 * Avoids using check_admin_referer().
-	 * This function might be called in different places,
-	 * and it can't cause it to die() if the nonce is invalid.
+	 * @since 0.7
+	 * @param ReflectionFunction|ReflectionMethod $reflection Reflection.
+	 * @return bool Whether there are parameters passed by reference.
+	 */
+	protected static function has_parameters_passed_by_reference( $reflection ) {
+		foreach ( $reflection->getParameters() as $parameter ) {
+			if ( $parameter->isPassedByReference() ) {
+				return true;
+			}
+		}
+		return false;
+	}
+
+	/**
+	 * Filters the output created by a shortcode callback.
 	 *
-	 * @return boolean $is_valid True if the nonce is valid.
+	 * @since 0.7
+	 *
+	 * @param string $output Shortcode output.
+	 * @param string $tag    Shortcode name.
+	 * @return string Output.
+	 * @global array $shortcode_tags
 	 */
-	public static function is_authorized() {
-		$nonce = isset( $_REQUEST['_wpnonce'] ) ? sanitize_text_field( wp_unslash( $_REQUEST['_wpnonce'] ) ) : ''; // WPCS: CSRF ok.
-		return ( self::has_cap() && ( false !== wp_verify_nonce( $nonce, 'update-post_' . get_the_ID() ) ) );
+	public static function decorate_shortcode_source( $output, $tag ) {
+		global $shortcode_tags;
+		if ( ! isset( $shortcode_tags[ $tag ] ) ) {
+			return $output;
+		}
+		$source = self::get_source( $shortcode_tags[ $tag ] );
+		if ( empty( $source ) ) {
+			return $output;
+		}
+		$source['shortcode'] = $tag;
+
+		$output = implode( '', array(
+			self::get_source_comment( $source, true ),
+			$output,
+			self::get_source_comment( $source, false ),
+		) );
+		return $output;
+	}
+
+	/**
+	 * Wraps output of a filter to add source stack comments.
+	 *
+	 * @param string $value Value.
+	 * @return string Value wrapped in source comments.
+	 */
+	public static function decorate_filter_source( $value ) {
+
+		// Abort if the output is not a string and it doesn't contain any HTML tags.
+		if ( ! is_string( $value ) || ! preg_match( '/<.+?>/s', $value ) ) {
+			return $value;
+		}
+
+		$post   = get_post();
+		$source = array(
+			'hook'   => current_filter(),
+			'filter' => true,
+		);
+		if ( $post ) {
+			$source['post_id']   = $post->ID;
+			$source['post_type'] = $post->post_type;
+		}
+		if ( isset( self::$current_hook_source_stack[ current_filter() ] ) ) {
+			$sources = self::$current_hook_source_stack[ current_filter() ];
+			array_pop( $sources ); // Remove self.
+			$source['sources'] = $sources;
+		}
+		return implode( '', array(
+			self::get_source_comment( $source, true ),
+			$value,
+			self::get_source_comment( $source, false ),
+		) );
 	}
 
 	/**
-	 * Adds an error message to the URL if it's not valid AMP.
+	 * Gets the plugin or theme of the callback, if one exists.
 	 *
-	 * When redirecting after saving a post, the content was validated for AMP compliance.
-	 * If it wasn't valid AMP, this will add a query arg to the URL.
-	 * And an error message will display on /wp-admin/post.php.
+	 * @param string|array $callback The callback for which to get the plugin.
+	 * @return array|null {
+	 *     The source data.
 	 *
-	 * @param string $url The URL of the redirect.
-	 * @return string $url The filtered URL, including the AMP error message query var.
+	 *     @type string $type Source type (core, plugin, mu-plugin, or theme).
+	 *     @type string $name Source name.
+	 *     @type string $function Normalized function name.
+	 *     @type ReflectionMethod|ReflectionFunction $reflection
+	 * }
 	 */
-	public static function error_message( $url ) {
-		$args = array(
-			self::ERROR_QUERY_KEY => self::ERROR_QUERY_VALUE,
-			self::ERROR_NONCE     => wp_create_nonce( self::ERROR_NONCE_ACTION ),
+	public static function get_source( $callback ) {
+		$reflection = null;
+		$class_name = null; // Because ReflectionMethod::getDeclaringClass() can return a parent class.
+		try {
+			if ( is_string( $callback ) && is_callable( $callback ) ) {
+				// The $callback is a function or static method.
+				$exploded_callback = explode( '::', $callback, 2 );
+				if ( 2 === count( $exploded_callback ) ) {
+					$class_name = $exploded_callback[0];
+					$reflection = new ReflectionMethod( $exploded_callback[0], $exploded_callback[1] );
+				} else {
+					$reflection = new ReflectionFunction( $callback );
+				}
+			} elseif ( is_array( $callback ) && isset( $callback[0], $callback[1] ) && method_exists( $callback[0], $callback[1] ) ) {
+				// The $callback is a method.
+				if ( is_string( $callback[0] ) ) {
+					$class_name = $callback[0];
+				} elseif ( is_object( $callback[0] ) ) {
+					$class_name = get_class( $callback[0] );
+				}
+				$reflection = new ReflectionMethod( $callback[0], $callback[1] );
+			} elseif ( is_object( $callback ) && ( 'Closure' === get_class( $callback ) ) ) {
+				$reflection = new ReflectionFunction( $callback );
+			}
+		} catch ( Exception $e ) {
+			return null;
+		}
+
+		if ( ! $reflection ) {
+			return null;
+		}
+
+		$source = compact( 'reflection' );
+
+		$file = $reflection->getFileName();
+		if ( $file ) {
+			$file         = wp_normalize_path( $file );
+			$slug_pattern = '([^/]+)';
+			if ( preg_match( ':' . preg_quote( trailingslashit( wp_normalize_path( WP_PLUGIN_DIR ) ), ':' ) . $slug_pattern . ':s', $file, $matches ) ) {
+				$source['type'] = 'plugin';
+				$source['name'] = $matches[1];
+			} elseif ( preg_match( ':' . preg_quote( trailingslashit( wp_normalize_path( get_theme_root() ) ), ':' ) . $slug_pattern . ':s', $file, $matches ) ) {
+				$source['type'] = 'theme';
+				$source['name'] = $matches[1];
+			} elseif ( preg_match( ':' . preg_quote( trailingslashit( wp_normalize_path( WPMU_PLUGIN_DIR ) ), ':' ) . $slug_pattern . ':s', $file, $matches ) ) {
+				$source['type'] = 'mu-plugin';
+				$source['name'] = $matches[1];
+			} elseif ( preg_match( ':' . preg_quote( trailingslashit( wp_normalize_path( ABSPATH ) ), ':' ) . '(wp-admin|wp-includes)/:s', $file, $matches ) ) {
+				$source['type'] = 'core';
+				$source['name'] = $matches[1];
+			}
+		}
+
+		if ( $class_name ) {
+			$source['function'] = $class_name . '::' . $reflection->getName();
+		} else {
+			$source['function'] = $reflection->getName();
+		}
+
+		return $source;
+	}
+
+	/**
+	 * Wraps a callback in comments if it outputs markup.
+	 *
+	 * If the sanitizer removes markup,
+	 * this indicates which plugin it was from.
+	 * The call_user_func_array() logic is mainly copied from WP_Hook:apply_filters().
+	 *
+	 * @param array $callback {
+	 *     The callback data.
+	 *
+	 *     @type callable $function
+	 *     @type int      $accepted_args
+	 *     @type array    $source
+	 * }
+	 * @return closure $wrapped_callback The callback, wrapped in comments.
+	 */
+	public static function wrapped_callback( $callback ) {
+		return function() use ( $callback ) {
+			global $wp_styles, $wp_scripts;
+
+			$function      = $callback['function'];
+			$accepted_args = $callback['accepted_args'];
+			$args          = func_get_args();
+
+			$before_styles_enqueued = array();
+			if ( isset( $wp_styles ) && isset( $wp_styles->queue ) ) {
+				$before_styles_enqueued = $wp_styles->queue;
+			}
+			$before_scripts_enqueued = array();
+			if ( isset( $wp_scripts ) && isset( $wp_scripts->queue ) ) {
+				$before_scripts_enqueued = $wp_scripts->queue;
+			}
+
+			ob_start();
+			$result = call_user_func_array( $function, array_slice( $args, 0, intval( $accepted_args ) ) );
+			$output = ob_get_clean();
+
+			// Keep track of which source enqueued the styles.
+			if ( isset( $wp_styles ) && isset( $wp_styles->queue ) ) {
+				foreach ( array_diff( $wp_styles->queue, $before_styles_enqueued ) as $handle ) {
+					AMP_Validation_Utils::$enqueued_style_sources[ $handle ][] = $callback['source'];
+				}
+			}
+
+			// Keep track of which source enqueued the scripts, and immediately report validity .
+			if ( isset( $wp_scripts ) && isset( $wp_scripts->queue ) ) {
+				foreach ( array_diff( $wp_scripts->queue, $before_scripts_enqueued ) as $handle ) {
+					AMP_Validation_Utils::$enqueued_script_sources[ $handle ][] = $callback['source'];
+
+					// Flag all scripts not loaded from the AMP CDN as validation errors.
+					if ( isset( $wp_scripts->registered[ $handle ] ) && 0 !== strpos( $wp_scripts->registered[ $handle ]->src, 'https://cdn.ampproject.org/' ) ) {
+						self::add_validation_error( array(
+							'code'       => self::ENQUEUED_SCRIPT_CODE,
+							'handle'     => $handle,
+							'dependency' => $wp_scripts->registered[ $handle ],
+							'sources'    => array(
+								$callback['source'],
+							),
+						) );
+					}
+				}
+			}
+
+			// Wrap output that contains HTML tags (as opposed to actions that trigger in HTML attributes).
+			if ( ! empty( $output ) && preg_match( '/<.+?>/s', $output ) ) {
+				echo AMP_Validation_Utils::get_source_comment( $callback['source'], true ); // WPCS: XSS ok.
+				echo $output; // WPCS: XSS ok.
+				echo AMP_Validation_Utils::get_source_comment( $callback['source'], false ); // WPCS: XSS ok.
+			}
+			return $result;
+		};
+	}
+
+	/**
+	 * Output a removed set, each wrapped in <code></code>.
+	 *
+	 * @param array[][] $set {
+	 *     The removed elements to output.
+	 *
+	 *     @type string $name  The name of the source.
+	 *     @type string $count The number that were invalid.
+	 * }
+	 * @return void
+	 */
+	protected static function output_removed_set( $set ) {
+		$items = array();
+		foreach ( $set as $name => $count ) {
+			if ( 1 === intval( $count ) ) {
+				$items[] = sprintf( '<code>%s</code>', esc_html( $name ) );
+			} else {
+				$items[] = sprintf( '<code>%s</code> (%d)', esc_html( $name ), $count );
+			}
+		}
+		echo implode( ', ', $items ); // WPCS: XSS OK.
+	}
+
+	/**
+	 * Whether to validate the front end response.
+	 *
+	 * Either the user has the capability and the query var is present.
+	 *
+	 * @return boolean Whether to validate.
+	 */
+	public static function should_validate_response() {
+		return self::has_cap() && isset( $_GET[ self::VALIDATE_QUERY_VAR ] ); // WPCS: CSRF ok.
+	}
+
+	/**
+	 * Finalize validation.
+	 *
+	 * @param DOMDocument $dom Document.
+	 * @param array       $args {
+	 *     Args.
+	 *
+	 *     @type bool $remove_source_comments           Whether source comments should be removed. Defaults to true.
+	 *     @type bool $send_validation_errors_header    Whether the X-AMP-Validation-Errors header should be sent. Defaults to true.
+	 *     @type bool $append_validation_status_comment Whether the validation errors should be appended as an HTML comment. Defaults to true.
+	 * }
+	 */
+	public static function finalize_validation( DOMDocument $dom, $args = array() ) {
+		$args = array_merge(
+			array(
+				'send_validation_errors_header'    => true,
+				'remove_source_comments'           => true,
+				'append_validation_status_comment' => true,
+			),
+			$args
 		);
-		return add_query_arg( $args, $url );
+
+		if ( $args['send_validation_errors_header'] && ! headers_sent() ) {
+			self::send_validation_errors_header();
+		}
+
+		if ( $args['remove_source_comments'] ) {
+			self::remove_source_comments( $dom );
+		}
+
+		if ( $args['append_validation_status_comment'] ) {
+			$report  = "\n# Validation Status\n";
+			$report .= "\n## Summary\n";
+			$report .= wp_json_encode( self::summarize_validation_errors( self::$validation_errors ), 128 /* JSON_PRETTY_PRINT */ ) . "\n";
+			$report .= "\n## Details\n";
+			$report .= wp_json_encode( self::$validation_errors, 128 /* JSON_PRETTY_PRINT */ ) . "\n";
+			$comment = $dom->createComment( $report );
+			$body    = $dom->getElementsByTagName( 'body' )->item( 0 );
+			if ( $body ) {
+				$body->appendChild( $comment );
+			}
+		}
 	}
 
 	/**
-	 * Displays an error message on /wp-admin/post.php if the saved content is not valid AMP.
+	 * Adds the validation callback if front-end validation is needed.
 	 *
-	 * Use $_GET, as get_query_var won't return the value.
-	 * This displays at the top of the 'Classic' editor.
+	 * @param array $sanitizers The AMP sanitizers.
+	 * @return array $sanitizers The filtered AMP sanitizers.
+	 */
+	public static function add_validation_callback( $sanitizers ) {
+		foreach ( $sanitizers as $sanitizer => $args ) {
+			$sanitizers[ $sanitizer ] = array_merge(
+				$args,
+				array(
+					'validation_error_callback' => __CLASS__ . '::add_validation_error',
+				)
+			);
+		}
+		return $sanitizers;
+	}
+
+	/**
+	 * Registers the post type to store the validation errors.
 	 *
 	 * @return void.
 	 */
-	public static function display_error() {
-		if ( ! isset( $_GET[ self::ERROR_QUERY_KEY ] ) ) {
-			return;
+	public static function register_post_type() {
+		$post_type = register_post_type(
+			self::POST_TYPE_SLUG,
+			array(
+				'labels'       => array(
+					'name'               => _x( 'Validation Status', 'post type general name', 'amp' ),
+					'singular_name'      => __( 'validation error', 'amp' ),
+					'not_found'          => __( 'No validation errors found', 'amp' ),
+					'not_found_in_trash' => __( 'No validation errors found in trash', 'amp' ),
+					'search_items'       => __( 'Search statuses', 'amp' ),
+					'edit_item'          => __( 'Validation Status', 'amp' ),
+				),
+				'supports'     => false,
+				'public'       => false,
+				'show_ui'      => true,
+				'show_in_menu' => AMP_Options_Manager::OPTION_NAME,
+			)
+		);
+
+		// Hide the add new post link.
+		$post_type->cap->create_posts = 'do_not_allow';
+	}
+
+	/**
+	 * Send validation errors back in response header.
+	 */
+	public static function send_validation_errors_header() {
+		header( self::VALIDATION_ERRORS_RESPONSE_HEADER_NAME . ': ' . wp_json_encode( self::$validation_errors ) );
+	}
+
+	/**
+	 * Stores the validation errors.
+	 *
+	 * After the preprocessors run, this gets the validation response if the query var is present.
+	 * It then stores the response in a custom post type.
+	 * If there's already an error post for the URL, but there's no error anymore, it deletes it.
+	 *
+	 * @param array  $validation_errors Validation errors.
+	 * @param string $url               URL on which the validation errors occurred.
+	 * @return int|null $post_id The post ID of the custom post type used, or null.
+	 * @global WP $wp
+	 */
+	public static function store_validation_errors( $validation_errors, $url ) {
+		$post_for_this_url = self::get_validation_status_post( $url );
+
+		// Since there are no validation errors and there is an existing $existing_post_id, just delete the post.
+		if ( empty( $validation_errors ) ) {
+			if ( $post_for_this_url ) {
+				wp_delete_post( $post_for_this_url->ID, true );
+			}
+			return null;
 		}
-		check_admin_referer( self::ERROR_NONCE_ACTION, self::ERROR_NONCE );
-		$error = isset( $_GET[ self::ERROR_QUERY_KEY ] ) ? sanitize_text_field( wp_unslash( $_GET[ self::ERROR_QUERY_KEY ] ) ) : ''; // WPCS: CSRF ok.
-		if ( self::ERROR_QUERY_VALUE === $error ) {
-			echo '<div class="notice notice-warning">';
-			printf( '<p>%s</p>', esc_html__( 'Warning: There is content which fails AMP validation; it will be stripped when served as AMP.', 'amp' ) );
-			if ( ! empty( $_GET['removed_elements'] ) && is_array( $_GET['removed_elements'] ) ) {
-				printf(
-					'<p>%s %s</p>',
-					esc_html__( 'Invalid elements:', 'amp' ),
-					'<code>' . implode( '</code>, <code>', array_map( 'esc_html', $_GET['removed_elements'] ) ) . '</code>'
-				);
+
+		$encoded_errors = wp_json_encode( $validation_errors );
+		$post_name      = md5( $encoded_errors );
+
+		// If the post name is unchanged then the errors are the same and there is nothing to do.
+		if ( $post_for_this_url && $post_for_this_url->post_name === $post_name ) {
+			return $post_for_this_url->ID;
+		}
+
+		// If there already exists a post for the given validation errors, just amend the $url to the existing post.
+		$post_for_other_url = get_page_by_path( $post_name, OBJECT, self::POST_TYPE_SLUG );
+		if ( ! $post_for_other_url ) {
+			$post_for_other_url = get_page_by_path( $post_name . '__trashed', OBJECT, self::POST_TYPE_SLUG );
+		}
+		if ( $post_for_other_url ) {
+			if ( 'trash' === $post_for_other_url->post_status ) {
+				wp_untrash_post( $post_for_other_url->ID );
 			}
-			if ( ! empty( $_GET['removed_attributes'] ) ) {
-				printf(
-					'<p>%s %s</p>',
-					esc_html__( 'Invalid attributes:', 'amp' ),
-					'<code>' . implode( '</code>, <code>', array_map( 'esc_html', $_GET['removed_attributes'] ) ) . '</code>'
+			if ( ! in_array( $url, get_post_meta( $post_for_other_url->ID, self::AMP_URL_META, false ), true ) ) {
+				add_post_meta( $post_for_other_url->ID, self::AMP_URL_META, wp_slash( $url ), false );
+			}
+			return $post_for_other_url->ID;
+		}
+
+		// Otherwise, create a new validation status post, or update the existing one.
+		$post_id = wp_insert_post( wp_slash( array(
+			'ID'           => $post_for_this_url ? $post_for_this_url->ID : null,
+			'post_type'    => self::POST_TYPE_SLUG,
+			'post_title'   => $url,
+			'post_name'    => $post_name,
+			'post_content' => $encoded_errors,
+			'post_status'  => 'publish',
+		) ) );
+		if ( ! $post_id ) {
+			return null;
+		}
+		if ( ! in_array( $url, get_post_meta( $post_id, self::AMP_URL_META, false ), true ) ) {
+			add_post_meta( $post_id, self::AMP_URL_META, wp_slash( $url ), false );
+		}
+		return $post_id;
+	}
+
+	/**
+	 * Gets the existing custom post that stores errors for the $url, if it exists.
+	 *
+	 * @param string $url The URL of the post.
+	 * @return WP_Post|null The post of the existing custom post, or null.
+	 */
+	public static function get_validation_status_post( $url ) {
+		if ( ! post_type_exists( self::POST_TYPE_SLUG ) ) {
+			return null;
+		}
+		$query = new WP_Query( array(
+			'post_type'      => self::POST_TYPE_SLUG,
+			'post_status'    => 'publish',
+			'posts_per_page' => 1,
+			'meta_query'     => array(
+				array(
+					'key'   => self::AMP_URL_META,
+					'value' => $url,
+				),
+			),
+		) );
+		return array_shift( $query->posts );
+	}
+
+	/**
+	 * Validates the latest published post.
+	 *
+	 * @return array|WP_Error The validation errors, or WP_Error.
+	 */
+	public static function validate_after_plugin_activation() {
+		$url = amp_admin_get_preview_permalink();
+		if ( ! $url ) {
+			return new WP_Error( 'no_published_post_url_available' );
+		}
+		$validation_errors = self::validate_url( $url );
+		if ( is_array( $validation_errors ) && count( $validation_errors ) > 0 ) {
+			self::store_validation_errors( $validation_errors, $url );
+			set_transient( self::PLUGIN_ACTIVATION_VALIDATION_ERRORS_TRANSIENT_KEY, $validation_errors, 60 );
+		} else {
+			delete_transient( self::PLUGIN_ACTIVATION_VALIDATION_ERRORS_TRANSIENT_KEY );
+		}
+		return $validation_errors;
+	}
+
+	/**
+	 * Validates a given URL.
+	 *
+	 * The validation errors will be stored in the validation status custom post type,
+	 * as well as in a transient.
+	 *
+	 * @param string $url The URL to validate.
+	 * @return array|WP_Error The validation errors, or WP_Error on error.
+	 */
+	public static function validate_url( $url ) {
+		$validation_url = add_query_arg(
+			array(
+				self::VALIDATE_QUERY_VAR   => 1,
+				self::CACHE_BUST_QUERY_VAR => wp_rand(),
+			),
+			$url
+		);
+
+		$r = wp_remote_get( $validation_url, array(
+			'cookies'   => wp_unslash( $_COOKIE ),
+			'sslverify' => false,
+			'headers'   => array(
+				'Cache-Control' => 'no-cache',
+			),
+		) );
+		if ( is_wp_error( $r ) ) {
+			return $r;
+		}
+		if ( wp_remote_retrieve_response_code( $r ) >= 400 ) {
+			return new WP_Error(
+				wp_remote_retrieve_response_code( $r ),
+				wp_remote_retrieve_response_message( $r )
+			);
+		}
+		$json = wp_remote_retrieve_header( $r, self::VALIDATION_ERRORS_RESPONSE_HEADER_NAME );
+		if ( ! $json ) {
+			return new WP_Error( 'response_header_absent' );
+		}
+		$validation_errors = json_decode( $json, true );
+		if ( ! is_array( $validation_errors ) ) {
+			return new WP_Error( 'malformed_json_validation_errors' );
+		}
+
+		return $validation_errors;
+	}
+
+	/**
+	 * On activating a plugin, display a notice if a plugin causes an AMP validation error.
+	 *
+	 * @return void
+	 */
+	public static function plugin_notice() {
+		global $pagenow;
+		if ( ( 'plugins.php' === $pagenow ) && ( ! empty( $_GET['activate'] ) || ! empty( $_GET['activate-multi'] ) ) ) { // WPCS: CSRF ok.
+			$validation_errors = get_transient( self::PLUGIN_ACTIVATION_VALIDATION_ERRORS_TRANSIENT_KEY );
+			if ( empty( $validation_errors ) || ! is_array( $validation_errors ) ) {
+				return;
+			}
+			delete_transient( self::PLUGIN_ACTIVATION_VALIDATION_ERRORS_TRANSIENT_KEY );
+			$errors          = self::summarize_validation_errors( $validation_errors );
+			$invalid_plugins = isset( $errors[ self::SOURCES_INVALID_OUTPUT ]['plugin'] ) ? array_unique( $errors[ self::SOURCES_INVALID_OUTPUT ]['plugin'] ) : null;
+			if ( isset( $invalid_plugins ) ) {
+				$reported_plugins = array();
+				foreach ( $invalid_plugins as $plugin ) {
+					$reported_plugins[] = sprintf( '<code>%s</code>', esc_html( $plugin ) );
+				}
+
+				$more_details_link = sprintf(
+					'<a href="%s">%s</a>',
+					esc_url( add_query_arg(
+						'post_type',
+						self::POST_TYPE_SLUG,
+						admin_url( 'edit.php' )
+					) ),
+					__( 'More details', 'amp' )
 				);
+				printf(
+					'<div class="notice notice-warning is-dismissible"><p>%s %s %s</p><button type="button" class="notice-dismiss"><span class="screen-reader-text">%s</span></button></div>',
+					esc_html( _n( 'Warning: The following plugin may be incompatible with AMP:', 'Warning: The following plugins may be incompatible with AMP: ', count( $invalid_plugins ), 'amp' ) ),
+					implode( ', ', $reported_plugins ),
+					$more_details_link,
+					esc_html__( 'Dismiss this notice.', 'amp' )
+				); // WPCS: XSS ok.
 			}
-			echo '</div>';
 		}
 	}
 
+	/**
+	 * Adds post columns to the UI for the validation errors.
+	 *
+	 * @param array $columns The post columns.
+	 * @return array $columns The new post columns.
+	 */
+	public static function add_post_columns( $columns ) {
+		$columns = array_merge(
+			$columns,
+			array(
+				'url_count'                  => esc_html__( 'Count', 'amp' ),
+				self::REMOVED_ELEMENTS       => esc_html__( 'Removed Elements', 'amp' ),
+				self::REMOVED_ATTRIBUTES     => esc_html__( 'Removed Attributes', 'amp' ),
+				self::SOURCES_INVALID_OUTPUT => esc_html__( 'Incompatible Sources', 'amp' ),
+			)
+		);
+
+		// Move date to end.
+		if ( isset( $columns['date'] ) ) {
+			$date = $columns['date'];
+			unset( $columns['date'] );
+			$columns['date'] = $date;
+		}
+
+		return $columns;
+	}
+
+	/**
+	 * Outputs custom columns in the /wp-admin UI for the AMP validation errors.
+	 *
+	 * @param string $column_name The name of the column.
+	 * @param int    $post_id     The ID of the post for the column.
+	 * @return void
+	 */
+	public static function output_custom_column( $column_name, $post_id ) {
+		$post = get_post( $post_id );
+		if ( self::POST_TYPE_SLUG !== $post->post_type ) {
+			return;
+		}
+		$validation_errors = json_decode( $post->post_content, true );
+		if ( ! is_array( $validation_errors ) ) {
+			return;
+		}
+		$errors = self::summarize_validation_errors( $validation_errors );
+		$urls   = get_post_meta( $post_id, self::AMP_URL_META, false );
+
+		switch ( $column_name ) {
+			case 'url_count':
+				echo count( $urls );
+				break;
+			case self::REMOVED_ELEMENTS:
+				if ( ! empty( $errors[ self::REMOVED_ELEMENTS ] ) ) {
+					self::output_removed_set( $errors[ self::REMOVED_ELEMENTS ] );
+				} else {
+					esc_html_e( '--', 'amp' );
+				}
+				break;
+			case self::REMOVED_ATTRIBUTES:
+				if ( ! empty( $errors[ self::REMOVED_ATTRIBUTES ] ) ) {
+					self::output_removed_set( $errors[ self::REMOVED_ATTRIBUTES ] );
+				} else {
+					esc_html_e( '--', 'amp' );
+				}
+				break;
+			case self::SOURCES_INVALID_OUTPUT:
+				if ( isset( $errors[ self::SOURCES_INVALID_OUTPUT ] ) ) {
+					$sources = array();
+					foreach ( $errors[ self::SOURCES_INVALID_OUTPUT ] as $type => $names ) {
+						foreach ( array_unique( $names ) as $name ) {
+							$sources[] = sprintf( '%s: <code>%s</code>', esc_html( $type ), esc_html( $name ) );
+						}
+					}
+					echo implode( ', ', $sources ); // WPCS: XSS ok.
+				}
+				break;
+		}
+	}
+
+	/**
+	 * Adds a 'Recheck' link to the edit.php row actions.
+	 *
+	 * The logic to add the new action is mainly copied from WP_Posts_List_Table::handle_row_actions().
+	 *
+	 * @param array   $actions The actions in the edit.php page.
+	 * @param WP_Post $post    The post for the actions.
+	 * @return array $actions The filtered actions.
+	 */
+	public static function filter_row_actions( $actions, $post ) {
+		if ( self::POST_TYPE_SLUG !== $post->post_type ) {
+			return $actions;
+		}
+
+		$actions['edit'] = sprintf(
+			'<a href="%s">%s</a>',
+			esc_url( get_edit_post_link( $post ) ),
+			esc_html__( 'Details', 'amp' )
+		);
+		unset( $actions['inline hide-if-no-js'] );
+		$url = get_post_meta( $post->ID, self::AMP_URL_META, true );
+
+		if ( ! empty( $url ) ) {
+			$actions[ self::RECHECK_ACTION ]  = self::get_recheck_link( $post, get_edit_post_link( $post->ID, 'raw' ), $url );
+			$actions[ self::DEBUG_QUERY_VAR ] = sprintf(
+				'<a href="%s" aria-label="%s">%s</a>',
+				esc_url( self::get_debug_url( $url ) ),
+				esc_attr__( 'Validate URL on frontend but without invalid elements/attributes removed', 'amp' ),
+				esc_html__( 'Debug', 'amp' )
+			);
+		}
+
+		return $actions;
+	}
+
+	/**
+	 * Adds a 'Recheck' bulk action to the edit.php page.
+	 *
+	 * @param array $actions The bulk actions in the edit.php page.
+	 * @return array $actions The filtered bulk actions.
+	 */
+	public static function add_bulk_action( $actions ) {
+		unset( $actions['edit'] );
+		$actions[ self::RECHECK_ACTION ] = esc_html__( 'Recheck', 'amp' );
+		return $actions;
+	}
+
+	/**
+	 * Handles the 'Recheck' bulk action on the edit.php page.
+	 *
+	 * @param string $redirect The URL of the redirect.
+	 * @param string $action   The action.
+	 * @param array  $items    The items on which to take the action.
+	 * @return string $redirect The filtered URL of the redirect.
+	 */
+	public static function handle_bulk_action( $redirect, $action, $items ) {
+		if ( self::RECHECK_ACTION !== $action ) {
+			return $redirect;
+		}
+		$remaining_invalid_urls = array();
+		foreach ( $items as $item ) {
+			$url = get_post_meta( $item, self::AMP_URL_META, true );
+			if ( empty( $url ) ) {
+				continue;
+			}
+
+			$validation_errors = self::validate_url( $url );
+			if ( ! is_array( $validation_errors ) ) {
+				continue;
+			}
+
+			self::store_validation_errors( $validation_errors, $url );
+			if ( ! empty( $validation_errors ) ) {
+				$remaining_invalid_urls[] = $url;
+			}
+		}
+
+		// Get the URLs that still have errors after rechecking.
+		$args = array(
+			self::URLS_TESTED      => count( $items ),
+			self::REMAINING_ERRORS => empty( $remaining_invalid_urls ) ? '0' : '1',
+		);
+
+		return add_query_arg( $args, $redirect );
+	}
+
+	/**
+	 * Outputs an admin notice after rechecking URL(s) on the custom post page.
+	 *
+	 * @return void
+	 */
+	public static function remaining_error_notice() {
+		if ( ! isset( $_GET[ self::REMAINING_ERRORS ] ) || self::POST_TYPE_SLUG !== get_current_screen()->post_type ) { // WPCS: CSRF ok.
+			return;
+		}
+
+		$count_urls_tested = isset( $_GET[ self::URLS_TESTED ] ) ? intval( $_GET[ self::URLS_TESTED ] ) : 1; // WPCS: CSRF ok.
+		$errors_remain     = ! empty( $_GET[ self::REMAINING_ERRORS ] ); // WPCS: CSRF ok.
+		if ( $errors_remain ) {
+			$class   = 'notice-warning';
+			$message = _n( 'The rechecked URL still has validation errors.', 'The rechecked URLs still have validation errors.', $count_urls_tested, 'amp' );
+		} else {
+			$message = _n( 'The rechecked URL has no validation errors.', 'The rechecked URLs have no validation errors.', $count_urls_tested, 'amp' );
+			$class   = 'updated';
+		}
+
+		printf(
+			'<div class="notice is-dismissible %s"><p>%s</p><button type="button" class="notice-dismiss"><span class="screen-reader-text">%s</span></button></div>',
+			esc_attr( $class ),
+			esc_html( $message ),
+			esc_html__( 'Dismiss this notice.', 'amp' )
+		);
+	}
+
+	/**
+	 * Handles clicking 'recheck' on the inline post actions.
+	 *
+	 * @param int $post_id The post ID of the recheck.
+	 * @return void
+	 */
+	public static function handle_inline_recheck( $post_id ) {
+		check_admin_referer( self::NONCE_ACTION . $post_id );
+		$url = get_post_meta( $post_id, self::AMP_URL_META, true );
+		if ( isset( $_GET['recheck_url'] ) ) {
+			$url = wp_validate_redirect( wp_unslash( $_GET['recheck_url'] ) );
+		}
+		$validation_errors = self::validate_url( $url );
+		$remaining_errors  = true;
+		if ( is_array( $validation_errors ) ) {
+			self::store_validation_errors( $validation_errors, $url );
+			$remaining_errors = ! empty( $validation_errors );
+		}
+
+		$redirect = wp_get_referer();
+		if ( ! $redirect || empty( $validation_errors ) ) {
+			// If there are no remaining errors and the post was deleted, redirect to edit.php instead of post.php.
+			$redirect = add_query_arg(
+				'post_type',
+				self::POST_TYPE_SLUG,
+				admin_url( 'edit.php' )
+			);
+		}
+		$args = array(
+			self::URLS_TESTED      => '1',
+			self::REMAINING_ERRORS => $remaining_errors ? '1' : '0',
+		);
+		wp_safe_redirect( add_query_arg( $args, $redirect ) );
+		exit();
+	}
+
+	/**
+	 * Removes the 'Publish' meta box from the CPT post.php page.
+	 *
+	 * @return void
+	 */
+	public static function remove_publish_meta_box() {
+		remove_meta_box( 'submitdiv', self::POST_TYPE_SLUG, 'side' );
+	}
+
+	/**
+	 * Adds the meta boxes to the CPT post.php page.
+	 *
+	 * @return void
+	 */
+	public static function add_meta_boxes() {
+		add_meta_box( self::VALIDATION_ERRORS_META_BOX, __( 'Validation Errors', 'amp' ), array( __CLASS__, 'print_validation_errors_meta_box' ), self::POST_TYPE_SLUG, 'normal' );
+		add_meta_box( self::STATUS_META_BOX, __( 'Status', 'amp' ), array( __CLASS__, 'print_status_meta_box' ), self::POST_TYPE_SLUG, 'side' );
+	}
+
+	/**
+	 * Outputs the markup of the side meta box in the CPT post.php page.
+	 *
+	 * This is partially copied from meta-boxes.php.
+	 * Adds 'Published on,' and links to move to trash and recheck.
+	 *
+	 * @param WP_Post $post The post for which to output the box.
+	 * @return void
+	 */
+	public static function print_status_meta_box( $post ) {
+		$redirect_url = add_query_arg(
+			'post',
+			$post->ID,
+			admin_url( 'post.php' )
+		);
+
+		echo '<div id="submitpost" class="submitbox">';
+		/* translators: Meta box date format */
+		$date_format = __( 'M j, Y @ H:i', 'default' );
+		echo '<div class="curtime misc-pub-section"><span id="timestamp">';
+		/* translators: %s: The date this was published */
+		printf( __( 'Published on: <b>%s</b>', 'amp' ), esc_html( date_i18n( $date_format, strtotime( $post->post_date ) ) ) ); // WPCS: XSS ok.
+		echo '</span></div>';
+		printf( '<div class="misc-pub-section"><a class="submitdelete deletion" href="%s">%s</a></div>', esc_url( get_delete_post_link( $post->ID ) ), esc_html__( 'Move to Trash', 'default' ) );
+
+		echo '<div class="misc-pub-section">';
+		echo self::get_recheck_link( $post, $redirect_url ); // WPCS: XSS ok.
+		$url = get_post_meta( $post->ID, self::AMP_URL_META, true );
+		if ( $url ) {
+			printf(
+				' | <a href="%s" aria-label="%s">%s</a>',
+				esc_url( self::get_debug_url( $url ) ),
+				esc_attr__( 'Validate URL on frontend but without invalid elements/attributes removed', 'amp' ),
+				esc_html__( 'Debug', 'amp' )
+			); // WPCS: XSS ok.
+		}
+		echo '</div>';
+
+		echo '</div><!-- /submitpost -->';
+	}
+
+	/**
+	 * Outputs the full meta box on the CPT post.php page.
+	 *
+	 * This displays the errors stored in the post content.
+	 * These are output as stored, but using <details> elements.
+	 *
+	 * @param WP_Post $post The post for which to output the box.
+	 * @return void
+	 */
+	public static function print_validation_errors_meta_box( $post ) {
+		$errors = json_decode( $post->post_content, true );
+		$urls   = get_post_meta( $post->ID, self::AMP_URL_META, false );
+		?>
+		<style>
+			.amp-validation-errors .detailed {
+				margin-left: 30px;
+			}
+			.amp-validation-errors .amp-recheck {
+				float: right;
+			}
+		</style>
+		<div class="amp-validation-errors">
+			<ul>
+				<?php foreach ( $errors as $error ) : ?>
+					<?php
+					$collasped_details = array();
+					?>
+					<li>
+						<details open>
+							<summary><code><?php echo esc_html( $error['code'] ); ?></code></summary>
+							<ul class="detailed">
+							<?php if ( self::INVALID_ELEMENT_CODE === $error['code'] ) : ?>
+								<li>
+									<details open>
+										<summary><?php esc_html_e( 'Removed:', 'amp' ); ?></summary>
+										<code class="detailed">
+											<?php
+											if ( isset( $error['parent_name'] ) ) {
+												echo esc_html( sprintf( '<%s …>', $error['parent_name'] ) );
+											}
+											?>
+											<mark>
+												<?php
+												echo esc_html( sprintf( '<%s', $error['node_name'] ) );
+												if ( isset( $error['node_attributes'] ) ) {
+													foreach ( $error['node_attributes'] as $key => $value ) {
+														printf( ' %s="%s"', esc_html( $key ), esc_html( $value ) );
+													}
+												}
+												echo esc_html( '>…' );
+												?>
+											</mark>
+										</code>
+									</details>
+									<?php
+									$collasped_details[] = 'node_attributes';
+									$collasped_details[] = 'node_name';
+									$collasped_details[] = 'parent_name';
+									?>
+								</li>
+							<?php elseif ( self::INVALID_ATTRIBUTE_CODE === $error['code'] ) : ?>
+								<li>
+									<details open>
+										<summary><?php esc_html_e( 'Removed:', 'amp' ); ?></summary>
+										<code class="detailed">
+											<?php
+											if ( isset( $error['parent_name'] ) ) {
+												echo esc_html( sprintf( '<%s', $error['parent_name'] ) );
+											}
+											foreach ( $error['element_attributes'] as $key => $value ) {
+												if ( $key === $error['node_name'] ) {
+													echo '<mark>';
+												}
+												printf( ' %s="%s"', esc_html( $key ), esc_html( $value ) );
+												if ( $key === $error['node_name'] ) {
+													echo '</mark>';
+												}
+											}
+											echo esc_html( '>' );
+											?>
+										</code>
+									</details>
+									<?php
+									$collasped_details[] = 'parent_name';
+									$collasped_details[] = 'element_attributes';
+									$collasped_details[] = 'node_name';
+									?>
+								</li>
+							<?php endif; ?>
+								<?php unset( $error['code'] ); ?>
+								<?php foreach ( $error as $key => $value ) : ?>
+									<li>
+										<details <?php echo ! in_array( $key, $collasped_details, true ) ? 'open' : ''; ?>>
+											<summary><code><?php echo esc_html( $key ); ?></code></summary>
+											<div class="detailed">
+												<?php if ( is_string( $value ) ) : ?>
+													<?php echo esc_html( $value ); ?>
+												<?php else : ?>
+													<pre><?php echo esc_html( wp_json_encode( $value, 128 /* JSON_PRETTY_PRINT */ | 64 /* JSON_UNESCAPED_SLASHES */ ) ); ?></pre>
+												<?php endif; ?>
+											</div>
+										</details>
+									</li>
+								<?php endforeach; ?>
+							</ul>
+						</details>
+					</li>
+				<?php endforeach; ?>
+			</ul>
+			<hr>
+			<h3><?php esc_html_e( 'URLs', 'amp' ); ?></h3>
+			<ul>
+				<?php foreach ( $urls as $url ) : ?>
+					<li>
+						<a href="<?php echo esc_url( $url ); ?>"><?php echo esc_url( $url ); ?></a>
+						<span class="amp-recheck">
+							<?php echo self::get_recheck_link( $post, get_edit_post_link( $post->ID, 'raw' ), $url ); // WPCS: XSS ok. ?>
+							|
+							<?php
+							printf(
+								'<a href="%s" aria-label="%s">%s</a>',
+								esc_url( self::get_debug_url( $url ) ),
+								esc_attr__( 'Validate URL on frontend but without invalid elements/attributes removed', 'amp' ),
+								esc_html__( 'Debug', 'amp' )
+							)
+							?>
+						</span>
+					</li>
+				<?php endforeach; ?>
+			</ul>
+		</div>
+		<?php
+	}
+
+	/**
+	 * Get validation debug UR:.
+	 *
+	 * @param string $url URL to to validate and debug.
+	 * @return string Debug URL.
+	 */
+	public static function get_debug_url( $url ) {
+		return add_query_arg(
+			array(
+				self::VALIDATE_QUERY_VAR => 1,
+				self::DEBUG_QUERY_VAR    => 1,
+			),
+			$url
+		) . '#development=1';
+	}
+
+	/**
+	 * Gets the link to recheck the post for AMP validity.
+	 *
+	 * Appends a query var to $redirect_url.
+	 * On clicking the link, it checks if errors still exist for $post.
+	 *
+	 * @param  WP_Post $post         The post storing the validation error.
+	 * @param  string  $redirect_url The URL of the redirect.
+	 * @param  string  $recheck_url  The URL to check. Optional.
+	 * @return string $link The link to recheck the post.
+	 */
+	public static function get_recheck_link( $post, $redirect_url, $recheck_url = null ) {
+		return sprintf(
+			'<a href="%s" aria-label="%s">%s</a>',
+			wp_nonce_url(
+				add_query_arg(
+					array(
+						'action'      => self::RECHECK_ACTION,
+						'recheck_url' => $recheck_url,
+					),
+					$redirect_url
+				),
+				self::NONCE_ACTION . $post->ID
+			),
+			esc_html__( 'Recheck the URL for AMP validity', 'amp' ),
+			esc_html__( 'Recheck', 'amp' )
+		);
+	}
+
 }
diff --git a/phpcs.xml b/phpcs.xml
index 312fc87d2aa..16c6f31e59f 100644
--- a/phpcs.xml
+++ b/phpcs.xml
@@ -28,7 +28,7 @@
 	</rule>
 	<rule ref="WordPress.NamingConventions.ValidVariableName">
 		<properties>
-			<property name="customPropertiesWhitelist" value="childNodes,tagName,textContent,parentNode,nodeType,nodeName,nextSibling,firstChild,nodeValue,DEFAULT_ARGS,documentElement,removeChild" />
+			<property name="customPropertiesWhitelist" value="childNodes,tagName,textContent,parentNode,nodeType,nodeName,nextSibling,firstChild,nodeValue,DEFAULT_ARGS,documentElement,removeChild,ownerDocument" />
 		</properties>
 	</rule>
 
diff --git a/phpunit.xml b/phpunit.xml
index a2b80c5bb36..4d7d8f842a4 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -22,6 +22,7 @@
 			<directory suffix=".php">./</directory>
 			<exclude>
 				<directory suffix=".php">dev-lib</directory>
+				<directory suffix=".php">svn</directory>
 				<directory suffix=".php">node_modules</directory>
 				<directory suffix=".php">tests</directory>
 				<directory suffix=".php">vendor</directory>
diff --git a/readme.md b/readme.md
index 8cdfb6070e5..b3fcd45f55d 100644
--- a/readme.md
+++ b/readme.md
@@ -16,13 +16,19 @@ Enable Accelerated Mobile Pages (AMP) on your WordPress site.
 
 ## Description ##
 
-This plugin adds support for the [Accelerated Mobile Pages](https://www.ampproject.org) (AMP) Project, which is an open source initiative that aims to provide mobile optimized content that can load instantly everywhere.
+Bring the speed and features of the open source [AMP project](https://www.ampproject.org/) to your site, the WordPress way.
 
-With the plugin active, all posts on your site will have dynamically generated AMP-compatible versions, accessible by appending `/amp/` to the end your post URLs. For example, if your post URL is `http://example.com/2016/01/01/amp-on/`, you can access the AMP version at `http://example.com/2016/01/01/amp-on/amp/`. If you do not have [pretty permalinks](https://codex.wordpress.org/Using_Permalinks#mod_rewrite:_.22Pretty_Permalinks.22) enabled, you can do the same thing by appending `?amp=1`, i.e. `http://example.com/?p=123&amp=1`
+With the plugin active, all posts on your site will have AMP-compatible versions, accessible by appending `/amp/` to the end your post URLs. For example, if your post URL is `http://example.com/2016/01/01/amp-on/`, you can access the AMP version at `http://example.com/2016/01/01/amp-on/amp/`. If you do not have [pretty permalinks](https://codex.wordpress.org/Using_Permalinks#mod_rewrite:_.22Pretty_Permalinks.22) enabled, you can do the same thing by appending `?amp=1`, i.e. `http://example.com/?p=123&amp=1`
 
-Note #1: homepage, the blog index, and archives are not currently supported.
+Also, your pages and custom post types can have AMP versions. Simply check their boxes on the 'AMP Settings' page in `/wp-admin`.
 
-Note #2: this plugin only creates AMP content but does not automatically display it to your users when they visit from a mobile device. That is handled by AMP consumers such as Google Search. For more details, see the [AMP Project FAQ](https://www.ampproject.org/docs/support/faqs.html).
+Your entire site can render as "Native AMP" if your theme calls `add_theme_support( 'amp' )`. There will only be one version of each URL: the AMP version. There won't be separate URLs with `/amp` or `?amp` appended. See this [wiki page](https://github.com/Automattic/amp-wp/wiki/Adding-Theme-Support#native-amp) for details and restrictions.
+
+Your theme can also use [Paired Mode](https://github.com/Automattic/amp-wp/wiki/Adding-Theme-Support#paired-mode), with your own custom templates for the AMP URLs.
+
+"Native AMP" and "Paired Mode" add full support for commenting and widgets.
+
+If your theme doesn't support `'amp'`, this will use basic legacy post templates for AMP consumers like Google Search and Twitter. And when visiting the site, the AMP content won't normally appear without appending strings to the URL like `/amp` or `?amp`.
 
 Follow along with or [contribute](https://github.com/Automattic/amp-wp/blob/develop/contributing.md) to the development of this plugin [on GitHub](https://github.com/Automattic/amp-wp). For more information on the plugin, how the plugin works and how to configure and extend it, please see the [project wiki](https://github.com/Automattic/amp-wp/wiki).
 
@@ -56,16 +62,48 @@ Follow along with or [contribute](https://github.com/Automattic/amp-wp/blob/deve
 
 ## Changelog ##
 
-### 0.7 (unreleased) ###
-- Add support for canonical AMP, if the theme registers support for it with `add_theme_support( 'amp' )`. See [#857](https://github.com/Automattic/amp-wp/pull/857), [#856](https://github.com/Automattic/amp-wp/pull/856). Props westonruter, kaitnyl, ThierryA.
+### 0.7.0 (unreleased) ###
+- Render an entire site as "Native AMP" if the theme calls `add_theme_support( 'amp' )`. See [#857](https://github.com/Automattic/amp-wp/pull/857), [#852](https://github.com/Automattic/amp-wp/pull/852), [#865](https://github.com/Automattic/amp-wp/pull/865), [#888](https://github.com/Automattic/amp-wp/pull/888). Props westonruter, kaitnyl, ThierryA.
+- Use the AMP spec to automatically discover the required AMP component scripts to include on the page while post-processing. See [#882](https://github.com/Automattic/amp-wp/pull/882), [#885](https://github.com/Automattic/amp-wp/pull/885). Props westonruter.
+- Automatically concatenate stylesheets from `style` tags with loaded stylesheets from `link` tags combined in one `style[amp-custom]`. See [#887](https://github.com/Automattic/amp-wp/pull/887), [#890](https://github.com/Automattic/amp-wp/pull/890), [#935](https://github.com/Automattic/amp-wp/pull/935). Props westonruter.
+- Update serialization to use HTML instead of XML; update minimum version of PHP fro, 5.2 to 5.3. See [#891](https://github.com/Automattic/amp-wp/pull/891).
+- Add support for widgets. See [#870](https://github.com/Automattic/amp-wp/pull/870). Props kienstra.
+- Add support for forms. See [#907](https://github.com/Automattic/amp-wp/pull/907), [#923](https://github.com/Automattic/amp-wp/pull/923). Props DavidCramer.
+- Use "Paired Mode" if the theme calls `add_theme_support( 'amp' )` and passes a `'template_dir'` value for the AMP templates. See [#856](https://github.com/Automattic/amp-wp/pull/856), [#877](https://github.com/Automattic/amp-wp/pull/877). Props westonruter, kaitnyl.
+- Add AMP implementations of audio/video playlists. See [#954](https://github.com/Automattic/amp-wp/pull/954). Props kienstra.
+- Allow full Customization when the theme supports `'amp'`. See [#952](https://github.com/Automattic/amp-wp/pull/952). Props westonruter.
 - Add support for all default WordPress widgets. See [#921](https://github.com/Automattic/amp-wp/pull/921), [#917](https://github.com/Automattic/amp-wp/pull/917). Props kienstra, westonruter.
 - Add support for more default embeds: Issuu, Post, Meetup, Reddit, Screencast, Tumblr, and WordPress Plugin Directory. See [#889](https://github.com/Automattic/amp-wp/pull/889). Props kaitnyl.
-- Allow native WordPress commenting, in fully valid AMP. See [#871](https://github.com/Automattic/amp-wp/pull/871), [#909](https://github.com/Automattic/amp-wp/pull/909). Props DavidCramer, westonruter.
+- Allow native WordPress commenting, in fully valid AMP. See [#1024](https://github.com/Automattic/amp-wp/pull/1024), [#1029](https://github.com/Automattic/amp-wp/pull/1029), [#871](https://github.com/Automattic/amp-wp/pull/871), [#909](https://github.com/Automattic/amp-wp/pull/909). Props DavidCramer, westonruter.
+- Add a UI for displaying validation errors, including invalid tags and attributes, with tracing for the source for each error according to which theme/plugin's shortcode, widget, or other hook is responsible. Includes debug mode to suspend sanitizer. See [#971](https://github.com/Automattic/amp-wp/pull/971), [#1012](https://github.com/Automattic/amp-wp/pull/1012), [#1016](https://github.com/Automattic/amp-wp/pull/1016). Props westonruter, kienstra.
+- On activating a plugin, validate a front-end page and display a notice if there were errors. See [#971](https://github.com/Automattic/amp-wp/pull/971). Props westonruter, kienstra.
 - Creation of AMP-related notifications, on entering invalid content in the 'classic' editor. See [#912](https://github.com/Automattic/amp-wp/pull/912/). Props kienstra, westonruter, ThierryA.
-- Add output buffering, ensuring the entire page is valid AMP. See [#929](https://github.com/Automattic/amp-wp/pull/929), [#857](https://github.com/Automattic/amp-wp/pull/857). Props westonruter, ThierryA.
-- Update the generated sanitizer file to the AMP spec, and simplify the file that generates it. See [#929](https://github.com/Automattic/amp-wp/pull/929). Props westonruter.
-
-See [0.7 milestone](https://github.com/Automattic/amp-wp/milestone/6?closed=1).
+- Optionally use `<amp-live-list>` to display comments, avoiding full-page refreshes on adding comments. And enable making requests for an `<amp-live-list>`, like for displaying posts. See [#1029](https://github.com/Automattic/amp-wp/pull/1029), [#915](https://github.com/Automattic/amp-wp/pull/915). Props DavidCramer, westonruter.
+- Support `<amp-bind>`, enabling more dynamic elements. See [#895](https://github.com/Automattic/amp-wp/pull/895). Props westonruter.
+- Add output buffering, ensuring the entire page is valid AMP. See [#929](https://github.com/Automattic/amp-wp/pull/929), [#857](https://github.com/Automattic/amp-wp/pull/857), [#931](https://github.com/Automattic/amp-wp/pull/931). Props westonruter, ThierryA.
+- Add validation of host names in URLs. See [#983](https://github.com/Automattic/amp-wp/pull/983). Props rubengonzalezmrf.
+- Add WP-CLI scripts to test AMP support of comments and widgets. See [#924](https://github.com/Automattic/amp-wp/pull/924), [#859](https://github.com/Automattic/amp-wp/pull/859). Props DavidCramer, kienstra.
+- Improve test coverage, including for `AMP_Theme_Support`. See [#1034](https://github.com/Automattic/amp-wp/pull/1034). Props DavidCramer, kienstra.
+- Update the generated sanitizer file to the AMP spec, and simplify the file that generates it. See [#929](https://github.com/Automattic/amp-wp/pull/929), [#926](https://github.com/Automattic/amp-wp/pull/926). Props westonruter.
+- Several sanitizer updates, including for styles, and preventing valid tags from being removed. See [#935](https://github.com/Automattic/amp-wp/pull/935), [#944](https://github.com/Automattic/amp-wp/pull/944), [#952](https://github.com/Automattic/amp-wp/pull/952). Props westonruter, davisshaver.
+- Improve sanitization of `<amp-img>`, `<amp-video>`, and `<amp-iframe>`. See [#937](https://github.com/Automattic/amp-wp/pull/937), [#1054](https://github.com/Automattic/amp-wp/pull/1054). Props kienstra, amedina.
+- Fix an issue where the JSON inside `<script type="application/json">` was wrapped with CDATA. See [#891](https://github.com/Automattic/amp-wp/pull/891). Props westonruter.
+- Allow use of AMP components outside of AMP documents, including in [PWA](https://developers.google.com/web/progressive-web-apps/). See [#1013](https://github.com/Automattic/amp-wp/pull/1013). Props westonruter.
+- Access the AMP query var with `amp_get_slug()`, instead of `AMP_QUERY_VAR`. See [#986](https://github.com/Automattic/amp-wp/pull/986). Props westonruter, mjangda.
+- Update build scripts, including PHP versions in `.travis.yml`. See [#1058](https://github.com/Automattic/amp-wp/pull/1058/), [#949](https://github.com/Automattic/amp-wp/pull/949). Props westonruter.
+- Prevent New Relic script from being injected in AMP responses. See [#932](https://github.com/Automattic/amp-wp/pull/932). Props westonruter.
+- Fix handling of 0 and empty height/width attributes. See [#979](https://github.com/Automattic/amp-wp/pull/979). Props davisshaver.
+
+For a full list of the closed issues and merged pull requests in this release, see the [0.7 milestone](https://github.com/Automattic/amp-wp/milestone/6?closed=1).
+
+Contributors in this release, including design, development, testing, and project management: Adam Silverstein (adamsilverstein), Alberto Medina (amedina), Christian Chung (christianc1), Claudio Sossi, David Cramer (DavidCramer), Davis Shaver (davisshaver), Douglas Paul (douglyuckling), Jason Johnston (jhnstn), Joshua Wold (jwold), Kaitlyn (kaitnyl), Leo Postovoit (postphotos), Mackenzie Hartung (MackenzieHartung), Maxim Siebert (MaximSiebert), Mike Crantea (mehigh), Mohammad Jangda (mjangda), Oscar Sanchez (oscarssanchez), Philip John (philipjohn), Renato Alves (renatonascalves), Rubén (rubengonzalezmrf), Ryan Kienstra (kienstra), Thierry Muller (ThierryA), vortfu, Weston Ruter (westonruter), Ziga Sancin (zigasancin).
+
+### 0.6.2 (2018-02-28) ###
+* Improve logic and use of escaping; limit flushing rewrite rules to only when supported_post_types change. See [#953](https://github.com/Automattic/amp-wp/pull/953). Props philipjohn, westonruter.
+* Fix AMP preview icon in Firefox. See [#920](https://github.com/Automattic/amp-wp/pull/920). Props zigasancin.
+
+### 0.6.1 (2018-02-09) ###
+Version bump to re-release plugin in order to deal with missing file in 0.6.0 release package that caused fatal error.
 
 ### 0.6.0 (2018-01-23) ###
 - Add support for the "page" post type. A new `page.php` is introduced with template parts factored out (`html-start.php`, `header.php`, `footer.php`, `html-end.php`) and re-used from `single.php`. Note that AMP URLs will end in `?amp` instead of `/amp/`. See [#825](https://github.com/Automattic/amp-wp/pull/825). Props technosailor, ThierryA, westonruter.
@@ -75,7 +113,7 @@ See [0.7 milestone](https://github.com/Automattic/amp-wp/milestone/6?closed=1).
 - Add generator meta tag for AMP. See [#810](https://github.com/Automattic/amp-wp/pull/810). Props vaporwavre.
 - Add code quality checking via phpcs, eslint, jscs, and jshint. See [#795](https://github.com/Automattic/amp-wp/pull/795). Props westonruter.
 - Add autoloader to reduce complexity. See [#828](https://github.com/Automattic/amp-wp/pull/828). Props mikeschinkel, westonruter, ThierryA.
-- Fix Polldaddy amd SoundCloud embeds. Add vanilla WordPress "embed" test page. A new `bin/create-embed-test-post.php` wp-cli script is introduced. See [#829](https://github.com/Automattic/amp-wp/pull/829). Props kienstra, westonruter, ThierryA.
+- Fix Polldaddy amd SoundCloud embeds. Add vanilla WordPress "embed" test page. A new `bin/create-embed-test-post.php` WP-CLI script is introduced. See [#829](https://github.com/Automattic/amp-wp/pull/829). Props kienstra, westonruter, ThierryA.
 - Merge AMP Customizer into main Customizer. See [#819](https://github.com/Automattic/amp-wp/pull/819). Props kaitnyl, westonruter.
 - Update AMP HTML tags and attributes. A new `bin/amphtml-update.sh` bash script is introduced. Fixes Playbuzz. See [#823](https://github.com/Automattic/amp-wp/pull/823). Props kienstra, ThierryA, westonruter.
 - Remove erroneous hash from id on amp-wp-header. See [#853](https://github.com/Automattic/amp-wp/pull/853). Props eshannon3.
diff --git a/readme.txt b/readme.txt
index fe723ec86f8..1f45c73947e 100644
--- a/readme.txt
+++ b/readme.txt
@@ -12,13 +12,19 @@ Enable Accelerated Mobile Pages (AMP) on your WordPress site.
 
 == Description ==
 
-This plugin adds support for the [Accelerated Mobile Pages](https://www.ampproject.org) (AMP) Project, which is an open source initiative that aims to provide mobile optimized content that can load instantly everywhere.
+Bring the speed and features of the open source [AMP project](https://www.ampproject.org/) to your site, the WordPress way.
 
-With the plugin active, all posts on your site will have dynamically generated AMP-compatible versions, accessible by appending `/amp/` to the end your post URLs. For example, if your post URL is `http://example.com/2016/01/01/amp-on/`, you can access the AMP version at `http://example.com/2016/01/01/amp-on/amp/`. If you do not have [pretty permalinks](https://codex.wordpress.org/Using_Permalinks#mod_rewrite:_.22Pretty_Permalinks.22) enabled, you can do the same thing by appending `?amp=1`, i.e. `http://example.com/?p=123&amp=1`
+With the plugin active, all posts on your site will have AMP-compatible versions, accessible by appending `/amp/` to the end your post URLs. For example, if your post URL is `http://example.com/2016/01/01/amp-on/`, you can access the AMP version at `http://example.com/2016/01/01/amp-on/amp/`. If you do not have [pretty permalinks](https://codex.wordpress.org/Using_Permalinks#mod_rewrite:_.22Pretty_Permalinks.22) enabled, you can do the same thing by appending `?amp=1`, i.e. `http://example.com/?p=123&amp=1`
 
-Note #1: homepage, the blog index, and archives are not currently supported.
+Also, your pages and custom post types can have AMP versions. Simply check their boxes on the 'AMP Settings' page in `/wp-admin`.
 
-Note #2: this plugin only creates AMP content but does not automatically display it to your users when they visit from a mobile device. That is handled by AMP consumers such as Google Search. For more details, see the [AMP Project FAQ](https://www.ampproject.org/docs/support/faqs.html).
+Your entire site can render as "Native AMP" if your theme calls `add_theme_support( 'amp' )`. There will only be one version of each URL: the AMP version. There won't be separate URLs with `/amp` or `?amp` appended. See this [wiki page](https://github.com/Automattic/amp-wp/wiki/Adding-Theme-Support#native-amp) for details and restrictions.
+
+Your theme can also use [Paired Mode](https://github.com/Automattic/amp-wp/wiki/Adding-Theme-Support#paired-mode), with your own custom templates for the AMP URLs.
+
+"Native AMP" and "Paired Mode" add full support for commenting and widgets.
+
+If your theme doesn't support `'amp'`, this will use basic legacy post templates for AMP consumers like Google Search and Twitter. And when visiting the site, the AMP content won't normally appear without appending strings to the URL like `/amp` or `?amp`.
 
 Follow along with or [contribute](https://github.com/Automattic/amp-wp/blob/develop/contributing.md) to the development of this plugin [on GitHub](https://github.com/Automattic/amp-wp). For more information on the plugin, how the plugin works and how to configure and extend it, please see the [project wiki](https://github.com/Automattic/amp-wp/wiki).
 
@@ -38,17 +44,51 @@ Follow along with or [contribute](https://github.com/Automattic/amp-wp/blob/deve
 
 == Changelog ==
 
-= 0.7 (unreleased) =
-
-- Add support for canonical AMP, if the theme registers support for it with `add_theme_support( 'amp' )`. See [#857](https://github.com/Automattic/amp-wp/pull/857), [#856](https://github.com/Automattic/amp-wp/pull/856). Props westonruter, kaitnyl, ThierryA.
+= 0.7.0 (unreleased) =
+
+- Render an entire site as "Native AMP" if the theme calls `add_theme_support( 'amp' )`. See [#857](https://github.com/Automattic/amp-wp/pull/857), [#852](https://github.com/Automattic/amp-wp/pull/852), [#865](https://github.com/Automattic/amp-wp/pull/865), [#888](https://github.com/Automattic/amp-wp/pull/888). Props westonruter, kaitnyl, ThierryA.
+- Use the AMP spec to automatically discover the required AMP component scripts to include on the page while post-processing. See [#882](https://github.com/Automattic/amp-wp/pull/882), [#885](https://github.com/Automattic/amp-wp/pull/885). Props westonruter.
+- Automatically concatenate stylesheets from `style` tags with loaded stylesheets from `link` tags combined in one `style[amp-custom]`. See [#887](https://github.com/Automattic/amp-wp/pull/887), [#890](https://github.com/Automattic/amp-wp/pull/890), [#935](https://github.com/Automattic/amp-wp/pull/935). Props westonruter.
+- Update serialization to use HTML instead of XML; update minimum version of PHP fro, 5.2 to 5.3. See [#891](https://github.com/Automattic/amp-wp/pull/891).
+- Add support for widgets. See [#870](https://github.com/Automattic/amp-wp/pull/870). Props kienstra.
+- Add support for forms. See [#907](https://github.com/Automattic/amp-wp/pull/907), [#923](https://github.com/Automattic/amp-wp/pull/923). Props DavidCramer.
+- Use "Paired Mode" if the theme calls `add_theme_support( 'amp' )` and passes a `'template_dir'` value for the AMP templates. See [#856](https://github.com/Automattic/amp-wp/pull/856), [#877](https://github.com/Automattic/amp-wp/pull/877). Props westonruter, kaitnyl.
+- Add AMP implementations of audio/video playlists. See [#954](https://github.com/Automattic/amp-wp/pull/954). Props kienstra.
+- Allow full Customization when the theme supports `'amp'`. See [#952](https://github.com/Automattic/amp-wp/pull/952). Props westonruter.
 - Add support for all default WordPress widgets. See [#921](https://github.com/Automattic/amp-wp/pull/921), [#917](https://github.com/Automattic/amp-wp/pull/917). Props kienstra, westonruter.
 - Add support for more default embeds: Issuu, Post, Meetup, Reddit, Screencast, Tumblr, and WordPress Plugin Directory. See [#889](https://github.com/Automattic/amp-wp/pull/889). Props kaitnyl.
-- Allow native WordPress commenting, in fully valid AMP. See [#871](https://github.com/Automattic/amp-wp/pull/871), [#909](https://github.com/Automattic/amp-wp/pull/909). Props DavidCramer, westonruter.
+- Allow native WordPress commenting, in fully valid AMP. See [#1024](https://github.com/Automattic/amp-wp/pull/1024), [#1029](https://github.com/Automattic/amp-wp/pull/1029), [#871](https://github.com/Automattic/amp-wp/pull/871), [#909](https://github.com/Automattic/amp-wp/pull/909). Props DavidCramer, westonruter.
+- Add a UI for displaying validation errors, including invalid tags and attributes, with tracing for the source for each error according to which theme/plugin's shortcode, widget, or other hook is responsible. Includes debug mode to suspend sanitizer. See [#971](https://github.com/Automattic/amp-wp/pull/971), [#1012](https://github.com/Automattic/amp-wp/pull/1012), [#1016](https://github.com/Automattic/amp-wp/pull/1016). Props westonruter, kienstra.
+- On activating a plugin, validate a front-end page and display a notice if there were errors. See [#971](https://github.com/Automattic/amp-wp/pull/971). Props westonruter, kienstra.
 - Creation of AMP-related notifications, on entering invalid content in the 'classic' editor. See [#912](https://github.com/Automattic/amp-wp/pull/912/). Props kienstra, westonruter, ThierryA.
-- Add output buffering, ensuring the entire page is valid AMP. See [#929](https://github.com/Automattic/amp-wp/pull/929), [#857](https://github.com/Automattic/amp-wp/pull/857). Props westonruter, ThierryA.
-- Update the generated sanitizer file to the AMP spec, and simplify the file that generates it. See [#929](https://github.com/Automattic/amp-wp/pull/929). Props westonruter.
+- Optionally use `<amp-live-list>` to display comments, avoiding full-page refreshes on adding comments. And enable making requests for an `<amp-live-list>`, like for displaying posts. See [#1029](https://github.com/Automattic/amp-wp/pull/1029), [#915](https://github.com/Automattic/amp-wp/pull/915). Props DavidCramer, westonruter.
+- Support `<amp-bind>`, enabling more dynamic elements. See [#895](https://github.com/Automattic/amp-wp/pull/895). Props westonruter.
+- Add output buffering, ensuring the entire page is valid AMP. See [#929](https://github.com/Automattic/amp-wp/pull/929), [#857](https://github.com/Automattic/amp-wp/pull/857), [#931](https://github.com/Automattic/amp-wp/pull/931). Props westonruter, ThierryA.
+- Add validation of host names in URLs. See [#983](https://github.com/Automattic/amp-wp/pull/983). Props rubengonzalezmrf.
+- Add WP-CLI scripts to test AMP support of comments and widgets. See [#924](https://github.com/Automattic/amp-wp/pull/924), [#859](https://github.com/Automattic/amp-wp/pull/859). Props DavidCramer, kienstra.
+- Improve test coverage, including for `AMP_Theme_Support`. See [#1034](https://github.com/Automattic/amp-wp/pull/1034). Props DavidCramer, kienstra.
+- Update the generated sanitizer file to the AMP spec, and simplify the file that generates it. See [#929](https://github.com/Automattic/amp-wp/pull/929), [#926](https://github.com/Automattic/amp-wp/pull/926). Props westonruter.
+- Several sanitizer updates, including for styles, and preventing valid tags from being removed. See [#935](https://github.com/Automattic/amp-wp/pull/935), [#944](https://github.com/Automattic/amp-wp/pull/944), [#952](https://github.com/Automattic/amp-wp/pull/952). Props westonruter, davisshaver.
+- Improve sanitization of `<amp-img>`, `<amp-video>`, and `<amp-iframe>`. See [#937](https://github.com/Automattic/amp-wp/pull/937), [#1054](https://github.com/Automattic/amp-wp/pull/1054). Props kienstra, amedina.
+- Fix an issue where the JSON inside `<script type="application/json">` was wrapped with CDATA. See [#891](https://github.com/Automattic/amp-wp/pull/891). Props westonruter.
+- Allow use of AMP components outside of AMP documents, including in [PWA](https://developers.google.com/web/progressive-web-apps/). See [#1013](https://github.com/Automattic/amp-wp/pull/1013). Props westonruter.
+- Access the AMP query var with `amp_get_slug()`, instead of `AMP_QUERY_VAR`. See [#986](https://github.com/Automattic/amp-wp/pull/986). Props westonruter, mjangda.
+- Update build scripts, including PHP versions in `.travis.yml`. See [#1058](https://github.com/Automattic/amp-wp/pull/1058/), [#949](https://github.com/Automattic/amp-wp/pull/949). Props westonruter.
+- Prevent New Relic script from being injected in AMP responses. See [#932](https://github.com/Automattic/amp-wp/pull/932). Props westonruter.
+- Fix handling of 0 and empty height/width attributes. See [#979](https://github.com/Automattic/amp-wp/pull/979). Props davisshaver.
+
+For a full list of the closed issues and merged pull requests in this release, see the [0.7 milestone](https://github.com/Automattic/amp-wp/milestone/6?closed=1).
+
+Contributors in this release, including design, development, testing, and project management: Adam Silverstein (adamsilverstein), Alberto Medina (amedina), Christian Chung (christianc1), Claudio Sossi, David Cramer (DavidCramer), Davis Shaver (davisshaver), Douglas Paul (douglyuckling), Jason Johnston (jhnstn), Joshua Wold (jwold), Kaitlyn (kaitnyl), Leo Postovoit (postphotos), Mackenzie Hartung (MackenzieHartung), Maxim Siebert (MaximSiebert), Mike Crantea (mehigh), Mohammad Jangda (mjangda), Oscar Sanchez (oscarssanchez), Philip John (philipjohn), Renato Alves (renatonascalves), Rubén (rubengonzalezmrf), Ryan Kienstra (kienstra), Thierry Muller (ThierryA), vortfu, Weston Ruter (westonruter), Ziga Sancin (zigasancin).
+
+= 0.6.2 (2018-02-28) =
+
+* Improve logic and use of escaping; limit flushing rewrite rules to only when supported_post_types change. See [#953](https://github.com/Automattic/amp-wp/pull/953). Props philipjohn, westonruter.
+* Fix AMP preview icon in Firefox. See [#920](https://github.com/Automattic/amp-wp/pull/920). Props zigasancin.
+
+= 0.6.1 (2018-02-09) =
 
-See [0.7 milestone](https://github.com/Automattic/amp-wp/milestone/6?closed=1).
+Version bump to re-release plugin in order to deal with missing file in 0.6.0 release package that caused fatal error.
 
 = 0.6.0 (2018-01-23) =
 
@@ -59,7 +99,7 @@ See [0.7 milestone](https://github.com/Automattic/amp-wp/milestone/6?closed=1).
 - Add generator meta tag for AMP. See [#810](https://github.com/Automattic/amp-wp/pull/810). Props vaporwavre.
 - Add code quality checking via phpcs, eslint, jscs, and jshint. See [#795](https://github.com/Automattic/amp-wp/pull/795). Props westonruter.
 - Add autoloader to reduce complexity. See [#828](https://github.com/Automattic/amp-wp/pull/828). Props mikeschinkel, westonruter, ThierryA.
-- Fix Polldaddy amd SoundCloud embeds. Add vanilla WordPress "embed" test page. A new `bin/create-embed-test-post.php` wp-cli script is introduced. See [#829](https://github.com/Automattic/amp-wp/pull/829). Props kienstra, westonruter, ThierryA.
+- Fix Polldaddy amd SoundCloud embeds. Add vanilla WordPress "embed" test page. A new `bin/create-embed-test-post.php` WP-CLI script is introduced. See [#829](https://github.com/Automattic/amp-wp/pull/829). Props kienstra, westonruter, ThierryA.
 - Merge AMP Customizer into main Customizer. See [#819](https://github.com/Automattic/amp-wp/pull/819). Props kaitnyl, westonruter.
 - Update AMP HTML tags and attributes. A new `bin/amphtml-update.sh` bash script is introduced. Fixes Playbuzz. See [#823](https://github.com/Automattic/amp-wp/pull/823). Props kienstra, ThierryA, westonruter.
 - Remove erroneous hash from id on amp-wp-header. See [#853](https://github.com/Automattic/amp-wp/pull/853). Props eshannon3.
diff --git a/tests/amp-tag-and-attribute-sanitizer-private-methods-tests.php b/tests/amp-tag-and-attribute-sanitizer-private-methods-tests.php
index be136c16bcb..a4286604307 100644
--- a/tests/amp-tag-and-attribute-sanitizer-private-methods-tests.php
+++ b/tests/amp-tag-and-attribute-sanitizer-private-methods-tests.php
@@ -991,7 +991,7 @@ public function get_validate_attr_spec_list_for_node_data() {
 						),
 					),
 				),
-				1,
+				2,
 			),
 			'attributes_allow_relative_false_fail' => array(
 				array(
@@ -1019,7 +1019,7 @@ public function get_validate_attr_spec_list_for_node_data() {
 						),
 					),
 				),
-				1,
+				2,
 			),
 			'attributes_allow_empty_false_fail' => array(
 				array(
diff --git a/tests/test-amp-analytics-options.php b/tests/test-amp-analytics-options.php
index 274934ffc45..5472864cedf 100644
--- a/tests/test-amp-analytics-options.php
+++ b/tests/test-amp-analytics-options.php
@@ -216,7 +216,7 @@ function test_two_analytics_components_added() {
 	/**
 	 * Test amp_get_analytics()
 	 *
-	 * @covers amp_get_analytics()
+	 * @covers \amp_get_analytics()
 	 */
 	public function test_amp_get_analytics() {
 		$this->insert_one_option(
@@ -243,7 +243,7 @@ public function test_amp_get_analytics() {
 	/**
 	 * Test amp_print_analytics()
 	 *
-	 * @covers amp_print_analytics()
+	 * @covers \amp_print_analytics()
 	 */
 	public function test_amp_print_analytics() {
 		$this->insert_one_option(
@@ -257,7 +257,34 @@ public function test_amp_print_analytics() {
 		amp_print_analytics( $analytics );
 		$output = ob_get_clean();
 
-		$this->assertEquals( 0, strpos( $output, '<amp-analytics' ) );
+		$this->assertStringStartsWith( '<amp-analytics', $output );
+		$this->assertContains( 'type="googleanalytics"><script type="application/json">{"requests":{"event":', $output );
+	}
+
+	/**
+	 * Test amp_print_analytics() when empty, called via wp_footer.
+	 *
+	 * Note that wp_footer action passes empty string to any handlers.
+	 * This test asserts that an issue discovered in PHP 7.1 is fixed.
+	 *
+	 * @see AMP_Theme_Support::add_hooks() Where add_action( 'wp_footer', 'amp_print_analytics' ) is done.
+	 * @covers \amp_print_analytics()
+	 */
+	public function test_amp_print_analytics_when_empty() {
+
+		ob_start();
+		amp_print_analytics( '' );
+		$this->assertEmpty( ob_get_clean() );
+
+		$this->insert_one_option(
+			$this->vendor,
+			$this->config_one
+		);
+		ob_start();
+		amp_print_analytics( '' );
+		$output = ob_get_clean();
+		$this->assertStringStartsWith( '<amp-analytics', $output );
+		$this->assertContains( 'type="googleanalytics"><script type="application/json">{"requests":{"event":', $output );
 	}
 
 }
diff --git a/tests/test-amp-audio-converter.php b/tests/test-amp-audio-converter.php
index 53d5cb246b1..2e24e2bc948 100644
--- a/tests/test-amp-audio-converter.php
+++ b/tests/test-amp-audio-converter.php
@@ -134,7 +134,7 @@ public function test_get_scripts__didnt_convert() {
 
 	public function test_get_scripts__did_convert() {
 		$source = '<audio width="400" height="300" src="https://example.com/audio/file.ogg"></audio>';
-		$expected = array( 'amp-audio' => 'https://cdn.ampproject.org/v0/amp-audio-latest.js' );
+		$expected = array( 'amp-audio' => true );
 
 		$dom = AMP_DOM_Utils::get_dom_from_content( $source );
 		$sanitizer = new AMP_Audio_Sanitizer( $dom );
diff --git a/tests/test-amp-dailymotion-embed.php b/tests/test-amp-dailymotion-embed.php
index 60eb1da4c03..54378a678dc 100644
--- a/tests/test-amp-dailymotion-embed.php
+++ b/tests/test-amp-dailymotion-embed.php
@@ -50,7 +50,7 @@ public function get_scripts_data() {
 			),
 			'converted' => array(
 				'https://www.dailymotion.com/video/x5awwth' . PHP_EOL,
-				array( 'amp-dailymotion' => 'https://cdn.ampproject.org/v0/amp-dailymotion-latest.js' ),
+				array( 'amp-dailymotion' => true ),
 			),
 		);
 	}
diff --git a/tests/test-amp-facebook-embed.php b/tests/test-amp-facebook-embed.php
index a0a1d453f8e..69a2be1f587 100644
--- a/tests/test-amp-facebook-embed.php
+++ b/tests/test-amp-facebook-embed.php
@@ -54,7 +54,7 @@ public function get_scripts_data() {
 			),
 			'converted' => array(
 				'https://www.facebook.com/zuck/posts/10102593740125791' . PHP_EOL,
-				array( 'amp-facebook' => 'https://cdn.ampproject.org/v0/amp-facebook-latest.js' ),
+				array( 'amp-facebook' => true ),
 			),
 		);
 	}
diff --git a/tests/test-amp-form-sanitizer.php b/tests/test-amp-form-sanitizer.php
index 9d1690d3620..954d0da4e94 100644
--- a/tests/test-amp-form-sanitizer.php
+++ b/tests/test-amp-form-sanitizer.php
@@ -99,7 +99,7 @@ public function test_converter( $source, $expected = null ) {
 	 */
 	public function test_scripts() {
 		$source   = '<form method="post" action-xhr="//example.org/example-page/" target="_top"></form>';
-		$expected = array( 'amp-form' => 'https://cdn.ampproject.org/v0/amp-form-latest.js' );
+		$expected = array( 'amp-form' => true );
 
 		$dom                 = AMP_DOM_Utils::get_dom_from_content( $source );
 		$whitelist_sanitizer = new AMP_Tag_And_Attribute_Sanitizer( $dom );
diff --git a/tests/test-amp-frontend-actions.php b/tests/test-amp-frontend-actions.php
new file mode 100644
index 00000000000..e2dd7d32241
--- /dev/null
+++ b/tests/test-amp-frontend-actions.php
@@ -0,0 +1,86 @@
+<?php
+/**
+ * Test AMP frontend actions.
+ *
+ * @package AMP
+ */
+
+/**
+ * Test functions in includes/amp-frontend-actions.php
+ */
+class Test_AMP_Frontend_Actions extends WP_UnitTestCase {
+
+	/**
+	 * Set up.
+	 */
+	public function setUp() {
+		parent::setUp();
+		amp_add_frontend_actions();
+	}
+
+	/**
+	 * After a test method runs, reset any state in WordPress the test method might have changed.
+	 */
+	public function tearDown() {
+		remove_theme_support( 'amp' );
+		parent::tearDown();
+	}
+
+	/**
+	 * Test that hook is added.
+	 *
+	 * @covers \amp_add_frontend_actions()
+	 */
+	public function test_has_hook() {
+		$this->assertEquals( 10, has_action( 'wp_head', 'amp_frontend_add_canonical' ) );
+	}
+
+	/**
+	 * URLs to test amphtml link.
+	 *
+	 * @return array
+	 */
+	public function get_amphtml_urls() {
+		$post_id = $this->factory()->post->create();
+		return array(
+			'home' => array(
+				home_url( '/' ),
+				add_query_arg( amp_get_slug(), '', home_url( '/' ) ),
+			),
+			'404'  => array(
+				home_url( '/no-existe/' ),
+				add_query_arg( amp_get_slug(), '', home_url( '/no-existe/' ) ),
+			),
+			'post' => array(
+				get_permalink( $post_id ),
+				amp_get_permalink( $post_id ),
+			),
+		);
+	}
+
+	/**
+	 * Adding link when theme support is not present.
+	 *
+	 * @dataProvider get_amphtml_urls
+	 * @covers \amp_frontend_add_canonical()
+	 * @param string $canonical_url Canonical URL.
+	 * @param string $amphtml_url   The amphtml URL.
+	 */
+	public function test_amp_frontend_add_canonical( $canonical_url, $amphtml_url ) {
+		$this->go_to( $canonical_url );
+		ob_start();
+		amp_frontend_add_canonical();
+		$output = ob_get_clean();
+		$this->assertEquals(
+			sprintf( '<link rel="amphtml" href="%s">', esc_url( $amphtml_url ) ),
+			$output
+		);
+
+		// Make sure adding the filter hides the amphtml link.
+		add_filter( 'amp_frontend_show_canonical', '__return_false' );
+		ob_start();
+		amp_frontend_add_canonical();
+		$output = ob_get_clean();
+		$this->assertEmpty( $output );
+	}
+}
diff --git a/tests/test-amp-helper-functions.php b/tests/test-amp-helper-functions.php
index 26a4963e27d..b29f3eefaa7 100644
--- a/tests/test-amp-helper-functions.php
+++ b/tests/test-amp-helper-functions.php
@@ -15,6 +15,8 @@ class Test_AMP_Helper_Functions extends WP_UnitTestCase {
 	 */
 	public function tearDown() {
 		remove_theme_support( 'amp' );
+		global $wp_scripts;
+		$wp_scripts = null;
 		parent::tearDown();
 	}
 
@@ -30,12 +32,22 @@ public function return_example_url( $url, $post_id ) {
 		return 'http://overridden.example.com/?' . build_query( compact( 'url', 'post_id', 'current_filter' ) );
 	}
 
+	/**
+	 * Test amp_get_slug().
+	 *
+	 * @covers \amp_get_slug()
+	 */
+	public function test_amp_get_slug() {
+		$this->assertSame( 'amp', amp_get_slug() );
+	}
+
 	/**
 	 * Test amp_get_permalink() without pretty permalinks.
 	 *
 	 * @covers \amp_get_permalink()
 	 */
 	public function test_amp_get_permalink_without_pretty_permalinks() {
+		remove_theme_support( 'amp' );
 		delete_option( 'permalink_structure' );
 		flush_rewrite_rules();
 
@@ -111,6 +123,40 @@ public function test_amp_get_permalink_with_pretty_permalinks() {
 		$this->assertContains( 'current_filter=amp_get_permalink', $url );
 	}
 
+	/**
+	 * Test amp_get_permalink() with theme support paired mode.
+	 *
+	 * @covers \amp_get_permalink()
+	 */
+	public function test_amp_get_permalink_with_theme_support() {
+		global $wp_rewrite;
+		add_theme_support( 'amp' );
+
+		update_option( 'permalink_structure', '/%year%/%monthnum%/%day%/%postname%/' );
+		$wp_rewrite->use_trailing_slashes = true;
+		$wp_rewrite->init();
+		$wp_rewrite->flush_rules();
+
+		$post_id = $this->factory()->post->create();
+		$this->assertEquals( get_permalink( $post_id ), amp_get_permalink( $post_id ) );
+
+		add_theme_support( 'amp', array(
+			'template_dir' => 'amp',
+		) );
+	}
+
+	/**
+	 * Test amp_remove_endpoint.
+	 *
+	 * @covers \amp_remove_endpoint()
+	 */
+	public function test_amp_remove_endpoint() {
+		$this->assertEquals( 'https://example.com/foo/', amp_remove_endpoint( 'https://example.com/foo/?amp' ) );
+		$this->assertEquals( 'https://example.com/foo/?#bar', amp_remove_endpoint( 'https://example.com/foo/?amp#bar' ) );
+		$this->assertEquals( 'https://example.com/foo/', amp_remove_endpoint( 'https://example.com/foo/amp/' ) );
+		$this->assertEquals( 'https://example.com/foo/?blaz', amp_remove_endpoint( 'https://example.com/foo/amp/?blaz' ) );
+	}
+
 	/**
 	 * Filter calls.
 	 *
@@ -132,10 +178,52 @@ public function capture_filter_call( $value ) {
 		return $value;
 	}
 
+	/**
+	 * Test script registering.
+	 *
+	 * @covers \amp_register_default_scripts()
+	 * @covers \amp_filter_script_loader_tag()
+	 * @global WP_Scripts $wp_scripts
+	 */
+	public function test_script_registering() {
+		global $wp_scripts;
+		$wp_scripts = null;
+		$this->assertEquals( 10, has_action( 'wp_default_scripts', 'amp_register_default_scripts' ) );
+		$this->assertEquals( PHP_INT_MAX, has_action( 'script_loader_tag', 'amp_filter_script_loader_tag' ) );
+
+		$this->assertTrue( wp_script_is( 'amp-runtime', 'registered' ) );
+		$this->assertTrue( wp_script_is( 'amp-mustache', 'registered' ) );
+		$this->assertTrue( wp_script_is( 'amp-list', 'registered' ) );
+		$this->assertTrue( wp_script_is( 'amp-bind', 'registered' ) );
+
+		wp_enqueue_script( 'amp-mathml' );
+		wp_enqueue_script( 'amp-mustache' );
+		$this->assertTrue( wp_script_is( 'amp-mathml', 'enqueued' ) );
+		$this->assertTrue( wp_script_is( 'amp-mustache', 'enqueued' ) );
+
+		// Try overriding URL.
+		wp_scripts()->registered['amp-mustache']->src = 'https://cdn.ampproject.org/v0/amp-mustache-0.1.js';
+
+		ob_start();
+		wp_print_scripts();
+		$output = ob_get_clean();
+
+		$this->assertStringStartsWith( '<script type=\'text/javascript\' src=\'https://cdn.ampproject.org/v0.js\' async></script>', $output ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
+		$this->assertContains( '<script type=\'text/javascript\' src=\'https://cdn.ampproject.org/v0/amp-mathml-latest.js\' async custom-element="amp-mathml"></script>', $output ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
+		$this->assertContains( '<script type=\'text/javascript\' src=\'https://cdn.ampproject.org/v0/amp-mustache-0.1.js\' async custom-template="amp-mustache"></script>', $output ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
+
+		// Try some experimental component to ensure expected script attributes are added.
+		wp_register_script( 'amp-foo', 'https://cdn.ampproject.org/v0/amp-foo-0.1.js', array( 'amp-runtime' ), null );
+		ob_start();
+		wp_print_scripts( 'amp-foo' );
+		$output = ob_get_clean();
+		$this->assertContains( '<script type=\'text/javascript\' src=\'https://cdn.ampproject.org/v0/amp-foo-0.1.js\' async custom-element="amp-foo"></script>', $output ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
+	}
+
 	/**
 	 * Test amp_get_content_embed_handlers().
 	 *
-	 * @covers amp_get_content_embed_handlers()
+	 * @covers \amp_get_content_embed_handlers()
 	 */
 	public function test_amp_get_content_embed_handlers() {
 		$post = $this->factory()->post->create_and_get();
@@ -161,7 +249,7 @@ public function test_amp_get_content_embed_handlers() {
 	/**
 	 * Test deprecated $post param for amp_get_content_embed_handlers().
 	 *
-	 * @covers amp_get_content_embed_handlers()
+	 * @covers \amp_get_content_embed_handlers()
 	 */
 	public function test_amp_get_content_embed_handlers_deprecated_param() {
 		$post = $this->factory()->post->create_and_get();
@@ -173,7 +261,7 @@ public function test_amp_get_content_embed_handlers_deprecated_param() {
 	/**
 	 * Test amp_get_content_sanitizers().
 	 *
-	 * @covers amp_get_content_sanitizers()
+	 * @covers \amp_get_content_sanitizers()
 	 */
 	public function test_amp_get_content_sanitizers() {
 		$post = $this->factory()->post->create_and_get();
@@ -211,7 +299,7 @@ public function test_amp_get_content_sanitizers() {
 	/**
 	 * Test deprecated $post param for amp_get_content_sanitizers().
 	 *
-	 * @covers amp_get_content_sanitizers()
+	 * @covers \amp_get_content_sanitizers()
 	 */
 	public function test_amp_get_content_sanitizers_deprecated_param() {
 		$post = $this->factory()->post->create_and_get();
@@ -226,7 +314,7 @@ public function test_amp_get_content_sanitizers_deprecated_param() {
 	 * @covers \post_supports_amp()
 	 */
 	public function test_post_supports_amp() {
-		add_post_type_support( 'page', AMP_QUERY_VAR );
+		add_post_type_support( 'page', amp_get_slug() );
 
 		// Test disabled by default for page for posts and show on front.
 		update_option( 'show_on_front', 'page' );
@@ -247,7 +335,7 @@ public function test_post_supports_amp() {
 		$this->assertFalse( post_supports_amp( $post ) );
 
 		// Reset.
-		remove_post_type_support( 'page', AMP_QUERY_VAR );
+		remove_post_type_support( 'page', amp_get_slug() );
 	}
 
 	/**
@@ -372,69 +460,4 @@ public function test_amp_get_schemaorg_metadata() {
 		$this->assertArrayHasKey( 'did_amp_schemaorg_metadata', $metadata );
 		$this->assertEquals( 'George', $metadata['author']['name'] );
 	}
-
-	/**
-	 * Test amp_intercept_post_request_redirect().
-	 *
-	 * @runInSeparateProcess
-	 * @preserveGlobalState disabled
-	 * @covers amp_intercept_post_request_redirect()
-	 */
-	public function test_amp_intercept_post_request_redirect() {
-		if ( ! function_exists( 'xdebug_get_headers' ) ) {
-			$this->markTestSkipped( 'xdebug is required for this test' );
-		}
-
-		add_theme_support( 'amp' );
-		$url = get_home_url();
-
-		add_filter( 'wp_doing_ajax', '__return_true' );
-		add_filter( 'wp_die_ajax_handler', function () {
-			return '__return_false';
-		} );
-
-		ob_start();
-		amp_intercept_post_request_redirect( $url );
-		$this->assertEquals( '{"success":true}', ob_get_clean() );
-
-		$this->assertContains( 'AMP-Redirect-To: ' . $url, xdebug_get_headers() );
-		$this->assertContains( 'Access-Control-Expose-Headers: AMP-Redirect-To', xdebug_get_headers() );
-
-		ob_start();
-		amp_intercept_post_request_redirect( '/new-location/' );
-		$this->assertEquals( '{"success":true}', ob_get_clean() );
-		$this->assertContains( 'AMP-Redirect-To: https://example.org/new-location/', xdebug_get_headers() );
-
-		ob_start();
-		amp_intercept_post_request_redirect( '//example.com/new-location/' );
-		$this->assertEquals( '{"success":true}', ob_get_clean() );
-		$headers = xdebug_get_headers();
-		$this->assertContains( 'AMP-Redirect-To: https://example.com/new-location/', $headers );
-
-		ob_start();
-		amp_intercept_post_request_redirect( '' );
-		$this->assertEquals( '{"success":true}', ob_get_clean() );
-		$this->assertContains( 'AMP-Redirect-To: https://example.org', xdebug_get_headers() );
-	}
-
-	/**
-	 * Test amp_handle_xhr_request().
-	 *
-	 * @runInSeparateProcess
-	 * @preserveGlobalState disabled
-	 * @covers amp_handle_xhr_headers_output()
-	 */
-	public function test_amp_handle_xhr_request() {
-		global $pagenow;
-		if ( ! function_exists( 'xdebug_get_headers' ) ) {
-			$this->markTestSkipped( 'xdebug is required for this test' );
-		}
-
-		$_GET['__amp_source_origin'] = 'https://example.org';
-		$pagenow                     = 'wp-comments-post.php';
-
-		amp_handle_xhr_request();
-		$this->assertContains( 'AMP-Access-Control-Allow-Source-Origin: https://example.org', xdebug_get_headers() );
-
-	}
 }
diff --git a/tests/test-amp-iframe-sanitizer.php b/tests/test-amp-iframe-sanitizer.php
index cf67b0f489f..be2f00becfd 100644
--- a/tests/test-amp-iframe-sanitizer.php
+++ b/tests/test-amp-iframe-sanitizer.php
@@ -10,57 +10,57 @@ public function get_data() {
 
 			'simple_iframe' => array(
 				'<iframe src="https://example.com/embed/132886713" width="500" height="281" frameborder="0" class="iframe-class" allowtransparency="false" allowfullscreen></iframe>',
-				'<amp-iframe style="max-width:100%" src="https://example.com/embed/132886713" width="500" height="281" frameborder="0" class="iframe-class amp-wp-enforced-sizes" allowfullscreen="" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw"></amp-iframe>',
+				'<amp-iframe src="https://example.com/embed/132886713" width="500" height="281" frameborder="0" class="iframe-class amp-wp-enforced-sizes" allowfullscreen="" sandbox="allow-scripts allow-same-origin" layout="intrinsic"></amp-iframe>',
 			),
 
 			'force_https' => array(
 				'<iframe src="http://example.com/embed/132886713" width="500" height="281" frameborder="0" class="iframe-class" allowtransparency="false" allowfullscreen></iframe>',
-				'<amp-iframe style="max-width:100%" src="https://example.com/embed/132886713" width="500" height="281" frameborder="0" class="iframe-class amp-wp-enforced-sizes" allowfullscreen="" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw"></amp-iframe>',
+				'<amp-iframe src="https://example.com/embed/132886713" width="500" height="281" frameborder="0" class="iframe-class amp-wp-enforced-sizes" allowfullscreen="" sandbox="allow-scripts allow-same-origin" layout="intrinsic"></amp-iframe>',
 			),
 
 			'iframe_without_dimensions' => array(
 				'<iframe src="https://example.com/video/132886713"></iframe>',
-				'<amp-iframe style="max-width:100%" src="https://example.com/video/132886713" sandbox="allow-scripts allow-same-origin" height="400" layout="fixed-height"></amp-iframe>',
+				'<amp-iframe src="https://example.com/video/132886713" sandbox="allow-scripts allow-same-origin" height="400" layout="fixed-height"></amp-iframe>',
 			),
 
 			'iframe_with_height_only' => array(
 				'<iframe src="https://example.com/video/132886713" height="400"></iframe>',
-				'<amp-iframe style="max-width:100%" src="https://example.com/video/132886713" height="400" sandbox="allow-scripts allow-same-origin" layout="fixed-height"></amp-iframe>',
+				'<amp-iframe src="https://example.com/video/132886713" height="400" sandbox="allow-scripts allow-same-origin" layout="fixed-height"></amp-iframe>',
 			),
 
 			'iframe_with_width_only' => array(
 				'<iframe src="https://example.com/video/132886713" width="600"></iframe>',
-				'<amp-iframe style="max-width:100%" src="https://example.com/video/132886713" sandbox="allow-scripts allow-same-origin" height="400" layout="fixed-height"></amp-iframe>',
+				'<amp-iframe src="https://example.com/video/132886713" sandbox="allow-scripts allow-same-origin" height="400" layout="fixed-height"></amp-iframe>',
 			),
 
 			'iframe_with_invalid_frameborder' => array(
 				'<iframe src="https://example.com/embed/132886713" width="500" height="281" frameborder="no"></iframe>',
-				'<amp-iframe style="max-width:100%" src="https://example.com/embed/132886713" width="500" height="281" frameborder="0" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe>',
+				'<amp-iframe src="https://example.com/embed/132886713" width="500" height="281" frameborder="0" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe>',
 			),
 
 			'iframe_with_1_frameborder' => array(
 				'<iframe src="https://example.com/embed/132886713" width="500" height="281" frameborder=1></iframe>',
-				'<amp-iframe style="max-width:100%" src="https://example.com/embed/132886713" width="500" height="281" frameborder="1" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe>',
+				'<amp-iframe src="https://example.com/embed/132886713" width="500" height="281" frameborder="1" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe>',
 			),
 
 			'simple_iframe_with_sandbox' => array(
 				'<iframe src="https://example.com/embed/132886713" width="500" height="281" sandbox="allow-same-origin"></iframe>',
-				'<amp-iframe style="max-width:100%" src="https://example.com/embed/132886713" width="500" height="281" sandbox="allow-same-origin" sizes="(min-width: 500px) 500px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe>',
+				'<amp-iframe src="https://example.com/embed/132886713" width="500" height="281" sandbox="allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe>',
 			),
 
 			'iframe_with_blacklisted_attribute' => array(
 				'<iframe src="https://example.com/embed/132886713" width="500" height="281" scrolling="auto"></iframe>',
-				'<amp-iframe style="max-width:100%" src="https://example.com/embed/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe>',
+				'<amp-iframe src="https://example.com/embed/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe>',
 			),
 
 			'iframe_with_sizes_attribute_is_overridden' => array(
-				'<iframe src="https://example.com/iframe" width="500" height="281" sizes="(min-width: 100px) 300px, 90vw"></iframe>',
-				'<amp-iframe style="max-width:100%" src="https://example.com/iframe" width="500" height="281" sizes="(min-width: 500px) 500px, 100vw" sandbox="allow-scripts allow-same-origin" class="amp-wp-enforced-sizes"></amp-iframe>',
+				'<iframe src="https://example.com/iframe" width="500" height="281"></iframe>',
+				'<amp-iframe src="https://example.com/iframe" width="500" height="281" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe>',
 			),
 
 			'iframe_with_protocol_relative_url' => array(
 				'<iframe src="//example.com/video/132886713"></iframe>',
-				'<amp-iframe style="max-width:100%" src="https://example.com/video/132886713" sandbox="allow-scripts allow-same-origin" height="400" layout="fixed-height"></amp-iframe>',
+				'<amp-iframe src="https://example.com/video/132886713" sandbox="allow-scripts allow-same-origin" height="400" layout="fixed-height"></amp-iframe>',
 			),
 
 			'multiple_same_iframe' => array(
@@ -69,7 +69,7 @@ public function get_data() {
 <iframe src="https://example.com/embed/132886713" width="500" height="281"></iframe>
 <iframe src="https://example.com/embed/132886713" width="500" height="281"></iframe>
 				',
-				'<amp-iframe style="max-width:100%" src="https://example.com/embed/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe><amp-iframe style="max-width:100%" src="https://example.com/embed/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe><amp-iframe style="max-width:100%" src="https://example.com/embed/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe>',
+				'<amp-iframe src="https://example.com/embed/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe><amp-iframe src="https://example.com/embed/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe><amp-iframe src="https://example.com/embed/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe>',
 			),
 
 			'multiple_different_iframes' => array(
@@ -78,19 +78,19 @@ public function get_data() {
 <iframe src="https://example.com/embed/67890" width="280" height="501"></iframe>
 <iframe src="https://example.com/embed/11111" width="700" height="601"></iframe>
 				',
-				'<amp-iframe style="max-width:100%" src="https://example.com/embed/12345" width="500" height="281" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe><amp-iframe style="max-width:100%" src="https://example.com/embed/67890" width="280" height="501" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 280px) 280px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe><amp-iframe style="max-width:100%" src="https://example.com/embed/11111" width="700" height="601" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 700px) 700px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe>',
+				'<amp-iframe src="https://example.com/embed/12345" width="500" height="281" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe><amp-iframe src="https://example.com/embed/67890" width="280" height="501" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe><amp-iframe src="https://example.com/embed/11111" width="700" height="601" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe>',
 			),
 			'iframe_in_p_tag' => array(
 				'<p><iframe src="https://example.com/video/132886713" width="500" height="281"></iframe></p>',
-				'<amp-iframe style="max-width:100%" src="https://example.com/video/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe>',
+				'<amp-iframe src="https://example.com/video/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe>',
 			),
 			'multiple_iframes_in_p_tag' => array(
 				'<p><iframe src="https://example.com/video/132886713" width="500" height="281"></iframe><iframe src="https://example.com/video/132886714" width="500" height="281"></iframe></p>',
-				'<amp-iframe style="max-width:100%" src="https://example.com/video/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe><amp-iframe style="max-width:100%" src="https://example.com/video/132886714" width="500" height="281" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe>',
+				'<amp-iframe src="https://example.com/video/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe><amp-iframe src="https://example.com/video/132886714" width="500" height="281" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe>',
 			),
 			'multiple_iframes_and_contents_in_p_tag' => array(
 				'<p>contents<iframe src="https://example.com/video/132886713" width="500" height="281"></iframe><iframe src="https://example.com/video/132886714" width="500" height="281"></iframe></p>',
-				'<p>contents</p><amp-iframe style="max-width:100%" src="https://example.com/video/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe><amp-iframe style="max-width:100%" src="https://example.com/video/132886714" width="500" height="281" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw" class="amp-wp-enforced-sizes"></amp-iframe>',
+				'<p>contents</p><amp-iframe src="https://example.com/video/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe><amp-iframe src="https://example.com/video/132886714" width="500" height="281" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"></amp-iframe>',
 			),
 		);
 	}
@@ -142,7 +142,7 @@ public function test_get_scripts__didnt_convert() {
 
 	public function test_get_scripts__did_convert() {
 		$source = '<iframe src="https://example.com/embed/132886713" width="500" height="281"></iframe>';
-		$expected = array( 'amp-iframe' => 'https://cdn.ampproject.org/v0/amp-iframe-latest.js' );
+		$expected = array( 'amp-iframe' => true );
 
 		$dom = AMP_DOM_Utils::get_dom_from_content( $source );
 		$sanitizer = new AMP_Iframe_Sanitizer( $dom );
@@ -160,7 +160,7 @@ public function test_get_scripts__did_convert() {
 
 	public function test__args__placeholder() {
 		$source = '<iframe src="https://example.com/video/132886713" width="500" height="281"></iframe>';
-		$expected = '<amp-iframe style="max-width:100%" src="https://example.com/video/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" sizes="(min-width: 500px) 500px, 100vw" class="amp-wp-enforced-sizes"><div placeholder="" class="amp-wp-iframe-placeholder"></div></amp-iframe>';
+		$expected = '<amp-iframe src="https://example.com/video/132886713" width="500" height="281" sandbox="allow-scripts allow-same-origin" layout="intrinsic" class="amp-wp-enforced-sizes"><div placeholder="" class="amp-wp-iframe-placeholder"></div></amp-iframe>';
 
 		$dom = AMP_DOM_Utils::get_dom_from_content( $source );
 		$sanitizer = new AMP_Iframe_Sanitizer( $dom, array(
diff --git a/tests/test-amp-img-sanitizer.php b/tests/test-amp-img-sanitizer.php
index 2c437b7deff..0f15018618c 100644
--- a/tests/test-amp-img-sanitizer.php
+++ b/tests/test-amp-img-sanitizer.php
@@ -12,81 +12,121 @@ public function setUp() {
 
 	public function get_data() {
 		return array(
-			'no_images' => array(
+			'no_images'                                => array(
 				'<p>Lorem Ipsum Demet Delorit.</p>',
 				'<p>Lorem Ipsum Demet Delorit.</p>',
 			),
 
-			'image_without_src' => array(
+			'image_without_src'                        => array(
 				'<p><img width="300" height="300" /></p>',
 				'<p></p>',
 			),
 
-			'image_with_empty_src' => array(
+			'image_with_empty_src'                     => array(
 				'<p><img src="" width="300" height="300" /></p>',
 				'<p></p>',
 			),
 
-			'image_with_self_closing_tag' => array(
+			'image_with_layout'                        => array(
+				'<img src="http://placehold.it/100x100" data-amp-layout="fill" width="100" height="100" />',
+				'<amp-img src="http://placehold.it/100x100" layout="fill" width="100" height="100" class="amp-wp-enforced-sizes"></amp-img>',
+			),
+
+			'image_with_spaces_only_src'               => array(
+				'<p><img src="    " width="300" height="300" /></p>',
+				'<p></p>',
+			),
+
+			'image_with_empty_width_and_height'        => array(
+				'<p><img src="http://placehold.it/300x300" width="" height="" /></p>',
+				'<p><amp-img src="http://placehold.it/300x300" width="600" height="400" class="amp-wp-unknown-size amp-wp-enforced-sizes" layout="intrinsic"></amp-img></p>',
+			),
+
+			'image_with_empty_width'                   => array(
+				'<p><img src="http://placehold.it/300x300" width="" height="300" /></p>',
+				'<p><amp-img src="http://placehold.it/300x300" width="600" height="300" class="amp-wp-unknown-size amp-wp-unknown-width amp-wp-enforced-sizes" layout="intrinsic"></amp-img></p>',
+			),
+
+			'image_with_empty_height'                  => array(
+				'<p><img src="http://placehold.it/300x300" width="300" height="" /></p>',
+				'<p><amp-img src="http://placehold.it/300x300" width="300" height="400" class="amp-wp-unknown-size amp-wp-unknown-height amp-wp-enforced-sizes" layout="intrinsic"></amp-img></p>',
+			),
+
+			'image_with_zero_width'                    => array(
+				'<p><img src="http://placehold.it/300x300" width="0" height="300" /></p>',
+				'<p><amp-img src="http://placehold.it/300x300" width="0" height="300" class="amp-wp-enforced-sizes"></amp-img></p>',
+			),
+
+			'image_with_zero_width_and_height'         => array(
+				'<p><img src="http://placehold.it/300x300" width="0" height="0" /></p>',
+				'<p><amp-img src="http://placehold.it/300x300" width="0" height="0" class="amp-wp-enforced-sizes"></amp-img></p>',
+			),
+
+			'image_with_decimal_width'                 => array(
+				'<p><img src="http://placehold.it/300x300" width="299.5" height="300" /></p>',
+				'<p><amp-img src="http://placehold.it/300x300" width="299.5" height="300" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img></p>',
+			),
+
+			'image_with_self_closing_tag'              => array(
 				'<img src="http://placehold.it/350x150" width="350" height="150" alt="Placeholder!" />',
-				'<amp-img src="http://placehold.it/350x150" width="350" height="150" alt="Placeholder!" sizes="(min-width: 350px) 350px, 100vw" class="amp-wp-enforced-sizes"></amp-img>',
+				'<amp-img src="http://placehold.it/350x150" width="350" height="150" alt="Placeholder!" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img>',
 			),
 
-			'image_with_no_end_tag' => array(
+			'image_with_no_end_tag'                    => array(
 				'<img src="http://placehold.it/350x150" width="350" height="150" alt="Placeholder!">',
-				'<amp-img src="http://placehold.it/350x150" width="350" height="150" alt="Placeholder!" sizes="(min-width: 350px) 350px, 100vw" class="amp-wp-enforced-sizes"></amp-img>',
+				'<amp-img src="http://placehold.it/350x150" width="350" height="150" alt="Placeholder!" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img>',
 			),
 
-			'image_with_end_tag' => array(
+			'image_with_end_tag'                       => array(
 				'<img src="http://placehold.it/350x150" width="350" height="150" alt="Placeholder!"></img>',
-				'<amp-img src="http://placehold.it/350x150" width="350" height="150" alt="Placeholder!" sizes="(min-width: 350px) 350px, 100vw" class="amp-wp-enforced-sizes"></amp-img>',
+				'<amp-img src="http://placehold.it/350x150" width="350" height="150" alt="Placeholder!" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img>',
 			),
 
-			'image_with_on_attribute' => array(
+			'image_with_on_attribute'                  => array(
 				'<img src="http://placehold.it/350x150" on="tap:my-lightbox" width="350" height="150" />',
-				'<amp-img src="http://placehold.it/350x150" on="tap:my-lightbox" width="350" height="150" sizes="(min-width: 350px) 350px, 100vw" class="amp-wp-enforced-sizes"></amp-img>',
+				'<amp-img src="http://placehold.it/350x150" on="tap:my-lightbox" width="350" height="150" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img>',
 			),
 
-			'image_with_blacklisted_attribute' => array(
+			'image_with_blacklisted_attribute'         => array(
 				'<img src="http://placehold.it/350x150" width="350" height="150" style="border: 1px solid red;" />',
-				'<amp-img src="http://placehold.it/350x150" width="350" height="150" sizes="(min-width: 350px) 350px, 100vw" class="amp-wp-enforced-sizes"></amp-img>',
+				'<amp-img src="http://placehold.it/350x150" width="350" height="150" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img>',
 			),
 
 			'image_with_no_dimensions_is_forced_dimensions' => array(
 				'<img src="http://placehold.it/350x150" />',
-				'<amp-img src="http://placehold.it/350x150" width="600" height="400" class="amp-wp-unknown-size amp-wp-enforced-sizes" sizes="(min-width: 600px) 600px, 100vw"></amp-img>',
+				'<amp-img src="http://placehold.it/350x150" width="600" height="400" class="amp-wp-unknown-size amp-wp-enforced-sizes" layout="intrinsic"></amp-img>',
 			),
 
 			'image_with_sizes_attribute_is_overridden' => array(
-				'<img src="http://placehold.it/350x150" width="350" height="150" sizes="(min-width: 100px) 300px, 90vw" />',
-				'<amp-img src="http://placehold.it/350x150" width="350" height="150" sizes="(min-width: 350px) 350px, 100vw" class="amp-wp-enforced-sizes"></amp-img>',
+				'<img src="http://placehold.it/350x150" width="350" height="150"  />',
+				'<amp-img src="http://placehold.it/350x150" width="350" height="150" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img>',
 			),
 
-			'gif_image_conversion' => array(
+			'gif_image_conversion'                     => array(
 				'<img src="http://placehold.it/350x150.gif" width="350" height="150" alt="Placeholder!" />',
-				'<amp-anim src="http://placehold.it/350x150.gif" width="350" height="150" alt="Placeholder!" sizes="(min-width: 350px) 350px, 100vw" class="amp-wp-enforced-sizes"></amp-anim>',
+				'<amp-anim src="http://placehold.it/350x150.gif" width="350" height="150" alt="Placeholder!" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-anim>',
 			),
 
-			'gif_image_url_with_querystring' => array(
+			'gif_image_url_with_querystring'           => array(
 				'<img src="http://placehold.it/350x150.gif?foo=bar" width="350" height="150" alt="Placeholder!" />',
-				'<amp-anim src="http://placehold.it/350x150.gif?foo=bar" width="350" height="150" alt="Placeholder!" sizes="(min-width: 350px) 350px, 100vw" class="amp-wp-enforced-sizes"></amp-anim>',
+				'<amp-anim src="http://placehold.it/350x150.gif?foo=bar" width="350" height="150" alt="Placeholder!" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-anim>',
 			),
 
-			'multiple_same_image' => array(
+			'multiple_same_image'                      => array(
 				'<img src="http://placehold.it/350x150" width="350" height="150" />
 <img src="http://placehold.it/350x150" width="350" height="150" />
 <img src="http://placehold.it/350x150" width="350" height="150" />
 <img src="http://placehold.it/350x150" width="350" height="150" />
 				',
-				'<amp-img src="http://placehold.it/350x150" width="350" height="150" sizes="(min-width: 350px) 350px, 100vw" class="amp-wp-enforced-sizes"></amp-img><amp-img src="http://placehold.it/350x150" width="350" height="150" sizes="(min-width: 350px) 350px, 100vw" class="amp-wp-enforced-sizes"></amp-img><amp-img src="http://placehold.it/350x150" width="350" height="150" sizes="(min-width: 350px) 350px, 100vw" class="amp-wp-enforced-sizes"></amp-img><amp-img src="http://placehold.it/350x150" width="350" height="150" sizes="(min-width: 350px) 350px, 100vw" class="amp-wp-enforced-sizes"></amp-img>',
+				'<amp-img src="http://placehold.it/350x150" width="350" height="150" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img><amp-img src="http://placehold.it/350x150" width="350" height="150" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img><amp-img src="http://placehold.it/350x150" width="350" height="150" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img><amp-img src="http://placehold.it/350x150" width="350" height="150" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img>',
 			),
 
-			'multiple_different_images' => array(
+			'multiple_different_images'                => array(
 				'<img src="http://placehold.it/350x150" width="350" height="150" />
 <img src="http://placehold.it/360x160" width="360" height="160" />
 <img src="http://placehold.it/370x170" width="370" height="170" />
 <img src="http://placehold.it/380x180" width="380" height="180" />',
-				'<amp-img src="http://placehold.it/350x150" width="350" height="150" sizes="(min-width: 350px) 350px, 100vw" class="amp-wp-enforced-sizes"></amp-img><amp-img src="http://placehold.it/360x160" width="360" height="160" sizes="(min-width: 360px) 360px, 100vw" class="amp-wp-enforced-sizes"></amp-img><amp-img src="http://placehold.it/370x170" width="370" height="170" sizes="(min-width: 370px) 370px, 100vw" class="amp-wp-enforced-sizes"></amp-img><amp-img src="http://placehold.it/380x180" width="380" height="180" sizes="(min-width: 380px) 380px, 100vw" class="amp-wp-enforced-sizes"></amp-img>',
+				'<amp-img src="http://placehold.it/350x150" width="350" height="150" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img><amp-img src="http://placehold.it/360x160" width="360" height="160" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img><amp-img src="http://placehold.it/370x170" width="370" height="170" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img><amp-img src="http://placehold.it/380x180" width="380" height="180" class="amp-wp-enforced-sizes" layout="intrinsic"></amp-img>',
 			),
 		);
 	}
@@ -122,7 +162,7 @@ public function test_no_gif_no_image_scripts() {
 
 	public function test_no_gif_image_scripts() {
 		$source = '<img src="http://placehold.it/350x150.gif" width="350" height="150" alt="Placeholder!" />';
-		$expected = array( 'amp-anim' => 'https://cdn.ampproject.org/v0/amp-anim-latest.js' );
+		$expected = array( 'amp-anim' => true );
 
 		$dom = AMP_DOM_Utils::get_dom_from_content( $source );
 		$sanitizer = new AMP_Img_Sanitizer( $dom );
diff --git a/tests/test-amp-instagram-embed.php b/tests/test-amp-instagram-embed.php
index 7035d77a3c7..9b28b056d8d 100644
--- a/tests/test-amp-instagram-embed.php
+++ b/tests/test-amp-instagram-embed.php
@@ -53,7 +53,7 @@ public function get_scripts_data() {
 			),
 			'converted' => array(
 				'https://instagram.com/p/7-l0z_p4A4/' . PHP_EOL,
-				array( 'amp-instagram' => 'https://cdn.ampproject.org/v0/amp-instagram-latest.js' ),
+				array( 'amp-instagram' => true ),
 			),
 		);
 	}
diff --git a/tests/test-amp-pinterest-embed.php b/tests/test-amp-pinterest-embed.php
index 857a77471bd..bfe36c86afb 100644
--- a/tests/test-amp-pinterest-embed.php
+++ b/tests/test-amp-pinterest-embed.php
@@ -37,7 +37,7 @@ public function get_scripts_data() {
 			),
 			'converted' => array(
 				'https://www.pinterest.com/pin/606156431067611861/' . PHP_EOL,
-				array( 'amp-pinterest' => 'https://cdn.ampproject.org/v0/amp-pinterest-latest.js' ),
+				array( 'amp-pinterest' => true ),
 			),
 		);
 	}
diff --git a/tests/test-amp-playbuzz-sanitizer.php b/tests/test-amp-playbuzz-sanitizer.php
index fcf85cc4a57..5988dcb9735 100644
--- a/tests/test-amp-playbuzz-sanitizer.php
+++ b/tests/test-amp-playbuzz-sanitizer.php
@@ -101,7 +101,7 @@ public function test_get_scripts__didnt_convert(){
 	 */
 	public function test_get_scripts__did_convert() {
 		$source   = '<div class="pb_feed" data-item="226dd4c0-ef13-4fee-850b-7be32bf6d121"></div>';
-		$expected = array( 'amp-playbuzz' => 'https://cdn.ampproject.org/v0/amp-playbuzz-latest.js' );
+		$expected = array( 'amp-playbuzz' => true );
 
 		$dom       = AMP_DOM_Utils::get_dom_from_content( $source );
 		$sanitizer = new AMP_Playbuzz_Sanitizer( $dom );
diff --git a/tests/test-amp-render-post.php b/tests/test-amp-render-post.php
index cce66cdeada..13fa8b7ec59 100644
--- a/tests/test-amp-render-post.php
+++ b/tests/test-amp-render-post.php
@@ -56,6 +56,18 @@ public function test__is_amp_endpoint() {
 		$this->assertFalse( $before_is_amp_endpoint, 'is_amp_endpoint was not defaulting to false before amp_render_post' );
 		$this->assertTrue( $this->was_amp_endpoint, 'is_amp_endpoint was not forced to true during amp_render_post' );
 		$this->assertFalse( $after_is_amp_endpoint, 'is_amp_endpoint was not reset after amp_render_post' );
+
+		add_theme_support( 'amp' );
+		$this->assertTrue( is_amp_endpoint() );
+
+		// Make is_admin() true, as requests for an admin page aren't for AMP endpoints.
+		set_current_screen( 'edit.php' );
+		$this->assertFalse( is_amp_endpoint() );
+		unset( $GLOBALS['current_screen'] );
+
+		$GLOBALS['wp_query']->is_feed = true;
+		$this->assertFalse( is_amp_endpoint() );
+		$GLOBALS['wp_query']->is_feed = false;
 	}
 
 	/**
diff --git a/tests/test-amp-soundcloud-embed.php b/tests/test-amp-soundcloud-embed.php
index cc7b1435478..389a8a4ebb0 100644
--- a/tests/test-amp-soundcloud-embed.php
+++ b/tests/test-amp-soundcloud-embed.php
@@ -162,7 +162,7 @@ public function get_scripts_data() {
 			),
 			'converted'     => array(
 				$this->oembed_url . PHP_EOL,
-				array( 'amp-soundcloud' => 'https://cdn.ampproject.org/v0/amp-soundcloud-latest.js' ),
+				array( 'amp-soundcloud' => true ),
 			),
 		);
 	}
diff --git a/tests/test-amp-style-sanitizer.php b/tests/test-amp-style-sanitizer.php
index c0190ec8811..7c708b42d29 100644
--- a/tests/test-amp-style-sanitizer.php
+++ b/tests/test-amp-style-sanitizer.php
@@ -57,10 +57,12 @@ public function get_body_style_attribute_data() {
 				),
 			),
 
-			'div_kses_banned_style' => array(
-				'<span style="overflow-x: hidden;">Specific overflow axis not allowed.</span>',
-				'<span>Specific overflow axis not allowed.</span>',
-				array(),
+			'span_display_none' => array(
+				'<span style="display: none;">Kses-banned properties are allowed since Kses will have already applied if user does not have unfiltered_html.</span>',
+				'<span class="amp-wp-inline-0f1bf07c72fdf1784fff2e164d9dca98">Kses-banned properties are allowed since Kses will have already applied if user does not have unfiltered_html.</span>',
+				array(
+					'.amp-wp-inline-0f1bf07c72fdf1784fff2e164d9dca98 { display:none; }',
+				),
 			),
 
 			'div_amp_banned_style' => array(
@@ -173,9 +175,9 @@ public function get_link_and_style_test_data() {
 				),
 			),
 			'style_with_no_head' => array(
-				'<html amp><body>Not good!<style>body{color:red}</style></body>',
+				'<html amp><body>Not good!<style>body{color:red;overflow:auto;overflow-x:scroll;overflow-y:scroll;}</style></body>',
 				array(
-					'body{color:red}',
+					'body{color:red;}',
 				),
 			),
 		);
diff --git a/tests/test-amp-twitter-embed.php b/tests/test-amp-twitter-embed.php
index e103701fade..b9cbf98c00d 100644
--- a/tests/test-amp-twitter-embed.php
+++ b/tests/test-amp-twitter-embed.php
@@ -66,7 +66,7 @@ public function get_scripts_data() {
 			),
 			'converted' => array(
 				'https://twitter.com/altjoen/status/118252236836061184' . PHP_EOL,
-				array( 'amp-twitter' => 'https://cdn.ampproject.org/v0/amp-twitter-latest.js' ),
+				array( 'amp-twitter' => true ),
 			),
 		);
 	}
diff --git a/tests/test-amp-video-sanitizer.php b/tests/test-amp-video-sanitizer.php
index f08f194db9e..5a0f989db05 100644
--- a/tests/test-amp-video-sanitizer.php
+++ b/tests/test-amp-video-sanitizer.php
@@ -10,42 +10,42 @@ public function get_data() {
 
 			'simple_video' => array(
 				'<video width="300" height="300" src="https://example.com/video.mp4"></video>',
-				'<amp-video style="max-width:100%" width="300" height="300" src="https://example.com/video.mp4" sizes="(min-width: 300px) 300px, 100vw" class="amp-wp-enforced-sizes"></amp-video>',
+				'<amp-video width="300" height="300" src="https://example.com/video.mp4" layout="responsive"></amp-video>',
 			),
 
 			'video_without_dimensions' => array(
 				'<video src="https://example.com/file.mp4"></video>',
-				'<amp-video style="max-width:100%" src="https://example.com/file.mp4" height="400" layout="fixed-height"></amp-video>',
+				'<amp-video src="https://example.com/file.mp4" height="400" layout="fixed-height"></amp-video>',
 			),
 
 			'autoplay_attribute' => array(
 				'<video width="300" height="300" src="https://example.com/video.mp4" autoplay></video>',
-				'<amp-video style="max-width:100%" width="300" height="300" src="https://example.com/video.mp4" autoplay="" sizes="(min-width: 300px) 300px, 100vw" class="amp-wp-enforced-sizes"></amp-video>',
+				'<amp-video width="300" height="300" src="https://example.com/video.mp4" autoplay="" layout="responsive"></amp-video>',
 			),
 
 			'autoplay_attribute__false' => array(
 				'<video width="300" height="300" src="https://example.com/video.mp4" autoplay="false"></video>',
-				'<amp-video style="max-width:100%" width="300" height="300" src="https://example.com/video.mp4" sizes="(min-width: 300px) 300px, 100vw" class="amp-wp-enforced-sizes"></amp-video>',
+				'<amp-video width="300" height="300" src="https://example.com/video.mp4" layout="responsive"></amp-video>',
 			),
 
 			'video_with_whitelisted_attributes__enabled' => array(
 				'<video width="300" height="300" src="https://example.com/video.mp4" controls loop="true" muted="muted"></video>',
-				'<amp-video style="max-width:100%" width="300" height="300" src="https://example.com/video.mp4" controls="" loop="" muted="" sizes="(min-width: 300px) 300px, 100vw" class="amp-wp-enforced-sizes"></amp-video>',
+				'<amp-video width="300" height="300" src="https://example.com/video.mp4" controls="" loop="" muted="" layout="responsive"></amp-video>',
 			),
 
 			'video_with_whitelisted_attributes__disabled' => array(
 				'<video width="300" height="300" src="https://example.com/video.mp4" controls="false" loop="false" muted="false"></video>',
-				'<amp-video style="max-width:100%" width="300" height="300" src="https://example.com/video.mp4" sizes="(min-width: 300px) 300px, 100vw" class="amp-wp-enforced-sizes"></amp-video>',
+				'<amp-video width="300" height="300" src="https://example.com/video.mp4" layout="responsive"></amp-video>',
 			),
 
 			'video_with_blacklisted_attribute' => array(
 				'<video width="300" height="300" src="https://example.com/video.mp4" style="border-color: red;"></video>',
-				'<amp-video style="max-width:100%" width="300" height="300" src="https://example.com/video.mp4" sizes="(min-width: 300px) 300px, 100vw" class="amp-wp-enforced-sizes"></amp-video>',
+				'<amp-video width="300" height="300" src="https://example.com/video.mp4" layout="responsive"></amp-video>',
 			),
 
 			'video_with_sizes_attribute_is_overridden' => array(
-				'<video width="300" height="200" src="https://example.com/file.mp4" sizes="(min-width: 100px) 200px, 90vw"></video>',
-				'<amp-video style="max-width:100%" width="300" height="200" src="https://example.com/file.mp4" sizes="(min-width: 300px) 300px, 100vw" class="amp-wp-enforced-sizes"></amp-video>',
+				'<video width="300" height="200" src="https://example.com/file.mp4"></video>',
+				'<amp-video width="300" height="200" src="https://example.com/file.mp4" layout="responsive"></amp-video>',
 			),
 
 			'video_with_children' => array(
@@ -53,7 +53,7 @@ public function get_data() {
 	<source src="https://example.com/video.mp4" type="video/mp4">
 	<source src="https://example.com/video.ogv" type="video/ogg">
 </video>',
-				'<amp-video style="max-width:100%" width="480" height="300" poster="https://example.com/video-image.gif" sizes="(min-width: 480px) 480px, 100vw" class="amp-wp-enforced-sizes"><source src="https://example.com/video.mp4" type="video/mp4"><source src="https://example.com/video.ogv" type="video/ogg"></amp-video>',
+				'<amp-video width="480" height="300" poster="https://example.com/video-image.gif" layout="responsive"><source src="https://example.com/video.mp4" type="video/mp4"><source src="https://example.com/video.ogv" type="video/ogg"></amp-video>',
 			),
 
 			'multiple_same_video' => array(
@@ -61,19 +61,19 @@ public function get_data() {
 <video src="https://example.com/video.mp4" width="480" height="300"></video>
 <video src="https://example.com/video.mp4" width="480" height="300"></video>
 <video src="https://example.com/video.mp4" width="480" height="300"></video>',
-				'<amp-video style="max-width:100%" src="https://example.com/video.mp4" width="480" height="300" sizes="(min-width: 480px) 480px, 100vw" class="amp-wp-enforced-sizes"></amp-video><amp-video style="max-width:100%" src="https://example.com/video.mp4" width="480" height="300" sizes="(min-width: 480px) 480px, 100vw" class="amp-wp-enforced-sizes"></amp-video><amp-video style="max-width:100%" src="https://example.com/video.mp4" width="480" height="300" sizes="(min-width: 480px) 480px, 100vw" class="amp-wp-enforced-sizes"></amp-video><amp-video style="max-width:100%" src="https://example.com/video.mp4" width="480" height="300" sizes="(min-width: 480px) 480px, 100vw" class="amp-wp-enforced-sizes"></amp-video>',
+				'<amp-video src="https://example.com/video.mp4" width="480" height="300" layout="responsive"></amp-video><amp-video src="https://example.com/video.mp4" width="480" height="300" layout="responsive"></amp-video><amp-video src="https://example.com/video.mp4" width="480" height="300" layout="responsive"></amp-video><amp-video src="https://example.com/video.mp4" width="480" height="300" layout="responsive"></amp-video>',
 			),
 
 			'multiple_different_videos' => array(
 				'<video src="https://example.com/video1.mp4" width="480" height="300"></video>
 <video src="https://example.com/video2.ogv" width="300" height="480"></video>
 <video src="https://example.com/video3.webm" height="100" width="200"></video>',
-				'<amp-video style="max-width:100%" src="https://example.com/video1.mp4" width="480" height="300" sizes="(min-width: 480px) 480px, 100vw" class="amp-wp-enforced-sizes"></amp-video><amp-video style="max-width:100%" src="https://example.com/video2.ogv" width="300" height="480" sizes="(min-width: 300px) 300px, 100vw" class="amp-wp-enforced-sizes"></amp-video><amp-video style="max-width:100%" src="https://example.com/video3.webm" height="100" width="200" sizes="(min-width: 200px) 200px, 100vw" class="amp-wp-enforced-sizes"></amp-video>',
+				'<amp-video src="https://example.com/video1.mp4" width="480" height="300" layout="responsive"></amp-video><amp-video src="https://example.com/video2.ogv" width="300" height="480" layout="responsive"></amp-video><amp-video src="https://example.com/video3.webm" height="100" width="200" layout="responsive"></amp-video>',
 			),
 
 			'https_not_required' => array(
 				'<video width="300" height="300" src="http://example.com/video.mp4"></video>',
-				'<amp-video style="max-width:100%" width="300" height="300" src="http://example.com/video.mp4" sizes="(min-width: 300px) 300px, 100vw" class="amp-wp-enforced-sizes"></amp-video>',
+				'<amp-video width="300" height="300" src="http://example.com/video.mp4" layout="responsive"></amp-video>',
 			),
 		);
 	}
@@ -123,7 +123,7 @@ public function test_get_scripts__didnt_convert() {
 
 	public function test_get_scripts__did_convert() {
 		$source = '<video width="300" height="300" src="https://example.com/video.mp4"></video>';
-		$expected = array( 'amp-video' => 'https://cdn.ampproject.org/v0/amp-video-latest.js' );
+		$expected = array( 'amp-video' => true );
 
 		$dom = AMP_DOM_Utils::get_dom_from_content( $source );
 		$sanitizer = new AMP_Video_Sanitizer( $dom );
diff --git a/tests/test-amp-vimeo-embed.php b/tests/test-amp-vimeo-embed.php
index e922f4eed02..41a1702e6c0 100644
--- a/tests/test-amp-vimeo-embed.php
+++ b/tests/test-amp-vimeo-embed.php
@@ -50,7 +50,7 @@ public function get_scripts_data() {
 			),
 			'converted' => array(
 				'https://vimeo.com/172355597' . PHP_EOL,
-				array( 'amp-vimeo' => 'https://cdn.ampproject.org/v0/amp-vimeo-latest.js' ),
+				array( 'amp-vimeo' => true ),
 			),
 		);
 	}
diff --git a/tests/test-amp-vine-embed.php b/tests/test-amp-vine-embed.php
index 0106e7106e9..862eb3b5ff8 100644
--- a/tests/test-amp-vine-embed.php
+++ b/tests/test-amp-vine-embed.php
@@ -33,7 +33,7 @@ public function get_scripts_data() {
 			),
 			'converted' => array(
 				'https://vine.co/v/MdKjXez002d' . PHP_EOL,
-				array( 'amp-vine' => 'https://cdn.ampproject.org/v0/amp-vine-latest.js' ),
+				array( 'amp-vine' => true ),
 			),
 		);
 	}
diff --git a/tests/test-amp-youtube-embed.php b/tests/test-amp-youtube-embed.php
index 747995412e5..be7ed6eb09e 100644
--- a/tests/test-amp-youtube-embed.php
+++ b/tests/test-amp-youtube-embed.php
@@ -55,7 +55,7 @@ public function get_scripts_data() {
 			),
 			'converted' => array(
 				'https://www.youtube.com/watch?v=kfVsfOSbJY0' . PHP_EOL,
-				array( 'amp-youtube' => 'https://cdn.ampproject.org/v0/amp-youtube-latest.js' ),
+				array( 'amp-youtube' => true ),
 			),
 		);
 	}
diff --git a/tests/test-amp.php b/tests/test-amp.php
index 19b68d9ad26..d78bc2edaab 100644
--- a/tests/test-amp.php
+++ b/tests/test-amp.php
@@ -21,7 +21,7 @@ public function tearDown() {
 	/**
 	 * Test amp_is_canonical().
 	 *
-	 * @covers amp_is_canonical()
+	 * @covers \amp_is_canonical()
 	 */
 	public function test_amp_is_canonical() {
 		remove_theme_support( 'amp' );
diff --git a/tests/test-class-amp-base-sanitizer.php b/tests/test-class-amp-base-sanitizer.php
index a7c6bcd8f08..8902bb297cf 100644
--- a/tests/test-class-amp-base-sanitizer.php
+++ b/tests/test-class-amp-base-sanitizer.php
@@ -1,127 +1,38 @@
 <?php
-
-class AMP_Base_Sanitizer__Enforce_Sizes_Attribute__Test extends WP_UnitTestCase {
-	public function get_data() {
-		return array(
-			'already_has_sizes' => array(
-				array(
-					'sizes' => 'blah',
-				),
-				array(
-					'sizes' => 'blah',
-				),
-			),
-
-			'empty' => array(
-				array(),
-				array(),
-			),
-
-			'no_width' => array(
-				array(
-					'height' => 100,
-				),
-				array(
-					'height' => 100,
-				),
-			),
-
-			'no_height' => array(
-				array(
-					'width' => 200,
-				),
-				array(
-					'width' => 200,
-				),
-			),
-
-			'enforce_sizes_no_class' => array(
-				array(
-					'width' => 200,
-					'height' => 100,
-				),
-				array(
-					'width' => 200,
-					'height' => 100,
-					'sizes' => '(min-width: 200px) 200px, 100vw',
-					'class' => 'amp-wp-enforced-sizes',
-				),
-			),
-
-			'enforce_sizes_has_class' => array(
-				array(
-					'width' => 200,
-					'height' => 100,
-					'class' => 'my-class',
-				),
-				array(
-					'width' => 200,
-					'height' => 100,
-					'sizes' => '(min-width: 200px) 200px, 100vw',
-					'class' => 'my-class amp-wp-enforced-sizes',
-				),
-			),
-
-			'enforce_sizes_with_bigger_content_max_width' => array(
-				array(
-					'width' => 250,
-					'height' => 100,
-				),
-				array(
-					'width' => 250,
-					'height' => 100,
-					'sizes' => '(min-width: 250px) 250px, 100vw',
-					'class' => 'amp-wp-enforced-sizes',
-				),
-				array(
-					'content_max_width' => 500,
-				),
-			),
-
-			'enforce_sizes_with_smaller_content_max_width' => array(
-				array(
-					'width' => 800,
-					'height' => 350,
-				),
-				array(
-					'width' => 800,
-					'height' => 350,
-					'sizes' => '(min-width: 675px) 675px, 100vw',
-					'class' => 'amp-wp-enforced-sizes',
-				),
-				array(
-					'content_max_width' => 675,
-				),
-			),
-		);
-	}
+/**
+ * Class AMP_Base_Sanitizer_Test
+ *
+ * @package AMP
+ */
+
+/**
+ * Test AMP_Base_Sanitizer_Test
+ *
+ * @covers AMP_Base_Sanitizer
+ */
+class AMP_Base_Sanitizer_Test extends WP_UnitTestCase {
 
 	/**
-	 * @dataProvider get_data
+	 * Gets data for test_set_layout().
+	 *
+	 * @return array
 	 */
-	public function test_enforce_sizes_attribute( $source_attributes, $expected_attributes, $args = array() ) {
-		$sanitizer = new AMP_Test_Stub_Sanitizer( new DOMDocument, $args );
-		$returned_attributes = $sanitizer->enforce_sizes_attribute( $source_attributes );
-
-		$this->assertEquals( $expected_attributes, $returned_attributes );
-	}
-}
-
-class AMP_Base_Sanitizer__Enforce_Fixed_Height__Test extends WP_UnitTestCase {
 	public function get_data() {
 		return array(
 			'both_dimensions_included' => array(
 				array(
-					'width' => 100,
+					'width'  => 100,
 					'height' => 100,
+					'layout' => 'responsive',
 				),
 				array(
-					'width' => 100,
+					'width'  => 100,
 					'height' => 100,
+					'layout' => 'responsive',
 				),
 			),
 
-			'both_dimensions_missing' => array(
+			'both_dimensions_missing'  => array(
 				array(),
 				array(
 					'height' => 400,
@@ -129,9 +40,9 @@ public function get_data() {
 				),
 			),
 
-			'both_dimensions_empty' => array(
+			'both_dimensions_empty'    => array(
 				array(
-					'width' => '',
+					'width'  => '',
 					'height' => '',
 				),
 				array(
@@ -140,7 +51,7 @@ public function get_data() {
 				),
 			),
 
-			'no_width' => array(
+			'no_width'                 => array(
 				array(
 					'height' => 100,
 				),
@@ -150,7 +61,7 @@ public function get_data() {
 				),
 			),
 
-			'no_height' => array(
+			'no_height'                => array(
 				array(
 					'width' => 200,
 				),
@@ -159,44 +70,63 @@ public function get_data() {
 					'layout' => 'fixed-height',
 				),
 			),
+
+			'no_layout_specified'      => array(
+				array(
+					'width'  => 100,
+					'height' => 100,
+				),
+				array(
+					'width'  => 100,
+					'height' => 100,
+				),
+			),
 		);
 	}
 
 	/**
+	 * Test AMP_Base_Sanitizer::set_layout().
+	 *
 	 * @dataProvider get_data
+	 * @param array $source_attributes   Source Attrs.
+	 * @param array $expected_attributes Expected Attrs.
+	 * @param array $args                Args.
+	 * @covers AMP_Base_Sanitizer::enforce_fixed_height()
 	 */
-	public function test_enforce_fixed_height( $source_attributes, $expected_attributes, $args = array() ) {
-		$sanitizer = new AMP_Test_Stub_Sanitizer( new DOMDocument, $args );
-		$returned_attributes = $sanitizer->enforce_fixed_height( $source_attributes );
-
+	public function test_set_layout( $source_attributes, $expected_attributes, $args = array() ) {
+		$sanitizer           = new AMP_Test_Stub_Sanitizer( new DOMDocument(), $args );
+		$returned_attributes = $sanitizer->set_layout( $source_attributes );
 		$this->assertEquals( $expected_attributes, $returned_attributes );
 	}
-}
 
-class AMP_Base_Sanitizer__Sanitize_Dimension__Test extends WP_UnitTestCase {
-	public function get_data() {
+	/**
+	 * Get sanitize_dimension data.
+	 *
+	 * @return array Data.
+	 */
+	public function get_sanitize_dimension_data() {
 		return array(
-			'empty' => array(
+			'empty'                => array(
 				array( '', 'width' ),
 				'',
 			),
 
-			'empty_space' => array(
+			'empty_space'          => array(
 				array( ' ', 'width' ),
 				'',
 			),
 
-			'int' => array(
+			'int'                  => array(
 				array( 123, 'width' ),
 				123,
 			),
 
-			'int_as_string' => array(
+			'int_as_string'        => array(
 				array( '123', 'width' ),
 				123,
 			),
 
-			'with_px' => array(
+			'with_px'              => array(
 				array( '567px', 'width' ),
 				567,
 			),
@@ -207,23 +137,23 @@ public function get_data() {
 				array( 'content_max_width' => 600 ),
 			),
 
-			'100%_width__no_max' => array(
+			'100%_width__no_max'   => array(
 				array( '100%', 'width' ),
 				'',
 			),
 
-			'50%_width__with_max' => array(
+			'50%_width__with_max'  => array(
 				array( '50%', 'width' ),
 				300,
 				array( 'content_max_width' => 600 ),
 			),
 
-			'%_height' => array(
+			'%_height'             => array(
 				array( '100%', 'height' ),
 				'',
 			),
 
-			'non_int' => array(
+			'non_int'              => array(
 				array( 'abcd', 'width' ),
 				'',
 			),
@@ -231,10 +161,16 @@ public function get_data() {
 	}
 
 	/**
-	 * @dataProvider get_data
+	 * Test AMP_Base_Sanitizer::sanitize_dimension().
+	 *
+	 * @param array $source_params  Source Attrs.
+	 * @param array $expected_value Expected Attrs.
+	 * @param array $args           Args.
+	 * @dataProvider get_sanitize_dimension_data
+	 * @covers AMP_Base_Sanitizer::sanitize_dimension()
 	 */
-	public function test_enforce_sizes_attribute( $source_params, $expected_value, $args = array() ) {
-		$sanitizer = new AMP_Test_Stub_Sanitizer( new DOMDocument, $args );
+	public function test_sanitize_dimension( $source_params, $expected_value, $args = array() ) {
+		$sanitizer                 = new AMP_Test_Stub_Sanitizer( new DOMDocument(), $args );
 		list( $value, $dimension ) = $source_params;
 
 		$actual_value = $sanitizer->sanitize_dimension( $value, $dimension );
@@ -245,26 +181,26 @@ public function test_enforce_sizes_attribute( $source_params, $expected_value, $
 	/**
 	 * Tests remove_child.
 	 *
-	 * @see AMP_Base_Sanitizer::remove_invalid_child()
+	 * @covers AMP_Base_Sanitizer::remove_invalid_child()
 	 */
 	public function test_remove_child() {
+		AMP_Validation_Utils::reset_validation_results();
 		$parent_tag_name = 'div';
-		$child_tag_name  = 'h1';
 		$dom_document    = new DOMDocument( '1.0', 'utf-8' );
 		$parent          = $dom_document->createElement( $parent_tag_name );
 		$child           = $dom_document->createElement( 'h1' );
 		$parent->appendChild( $child );
 
-		// To ignore WordPress.NamingConventions.ValidVariableName.NotSnakeCaseMemberVar.
-		// @codingStandardsIgnoreStart
-
 		$this->assertEquals( $child, $parent->firstChild );
-		$sanitizer = new AMP_Iframe_Sanitizer( $dom_document, array(
-			'remove_invalid_callback' => 'AMP_Validation_Utils::track_removed',
-		) );
+		$sanitizer = new AMP_Iframe_Sanitizer(
+			$dom_document, array(
+				'validation_error_callback' => 'AMP_Validation_Utils::add_validation_error',
+			)
+		);
 		$sanitizer->remove_invalid_child( $child );
 		$this->assertEquals( null, $parent->firstChild );
-		$this->assertEquals( 1, AMP_Validation_Utils::$removed_nodes[ $child_tag_name ] );
+		$this->assertCount( 1, AMP_Validation_Utils::$validation_errors );
+		$this->assertEquals( $child->nodeName, AMP_Validation_Utils::$validation_errors[0]['node_name'] );
 
 		$parent->appendChild( $child );
 		$this->assertEquals( $child, $parent->firstChild );
@@ -272,37 +208,40 @@ public function test_remove_child() {
 
 		$this->assertEquals( null, $parent->firstChild );
 		$this->assertEquals( null, $child->parentNode );
-		// @codingStandardsIgnoreEnd
-		AMP_Validation_Utils::$removed_nodes = null;
+		AMP_Validation_Utils::$validation_errors = null;
 	}
 
 	/**
 	 * Tests remove_child.
 	 *
-	 * @see AMP_Base_Sanitizer::remove_invalid_child()
+	 * @covers AMP_Base_Sanitizer::remove_invalid_child()
 	 */
 	public function test_remove_attribute() {
-		AMP_Validation_Utils::reset_removed();
+		AMP_Validation_Utils::reset_validation_results();
 		$video_name   = 'amp-video';
 		$attribute    = 'onload';
 		$dom_document = new DOMDocument( '1.0', 'utf-8' );
 		$video        = $dom_document->createElement( $video_name );
 		$video->setAttribute( $attribute, 'someFunction()' );
-
-		// To ignore WordPress.NamingConventions.ValidVariableName.NotSnakeCaseMemberVar.
-		// @codingStandardsIgnoreStart
-		$args = array(
-			'remove_invalid_callback' => 'AMP_Validation_Utils::track_removed',
-		);
-		$expected_removed = array(
-			$attribute => 1,
+		$attr_node = $video->getAttributeNode( $attribute );
+		$args      = array(
+			'validation_error_callback' => 'AMP_Validation_Utils::add_validation_error',
 		);
 		$sanitizer = new AMP_Video_Sanitizer( $dom_document, $args );
 		$sanitizer->remove_invalid_attribute( $video, $attribute );
 		$this->assertEquals( null, $video->getAttribute( $attribute ) );
-		$this->assertEquals( $expected_removed, AMP_Validation_Utils::$removed_attributes );
-		// @codingStandardsIgnoreEnd
-		AMP_Validation_Utils::reset_removed();
+		$this->assertEquals(
+			array(
+				'code'               => AMP_Validation_Utils::INVALID_ATTRIBUTE_CODE,
+				'node_name'          => $attr_node->nodeName,
+				'parent_name'        => $video->nodeName,
+				'sources'            => array(),
+				'element_attributes' => array(
+					'onload' => 'someFunction()',
+				),
+			),
+			AMP_Validation_Utils::$validation_errors[0]
+		);
+		AMP_Validation_Utils::reset_validation_results();
 	}
-
 }
diff --git a/tests/test-class-amp-comment-walker.php b/tests/test-class-amp-comment-walker.php
new file mode 100644
index 00000000000..1e13edb8c8b
--- /dev/null
+++ b/tests/test-class-amp-comment-walker.php
@@ -0,0 +1,129 @@
+<?php
+/**
+ * Tests for AMP_Comment_Walker class.
+ *
+ * @package AMP
+ */
+
+/**
+ * Tests for AMP_Comment_Walker class.
+ *
+ * @since 0.7
+ */
+class Test_AMP_Comment_Walker extends WP_UnitTestCase {
+
+	/**
+	 * The comment walker.
+	 *
+	 * @var AMP_Comment_Walker
+	 */
+	public $walker;
+
+	/**
+	 * Setup.
+	 *
+	 * @inheritdoc
+	 */
+	public function setUp() {
+		parent::setUp();
+		$this->walker = new AMP_Comment_Walker();
+	}
+
+	/**
+	 * Test AMP_Comment_Walker::start_el.
+	 *
+	 * @covers AMP_Comment_Walker::start_el()
+	 */
+	public function test_start_el() {
+		$GLOBALS['post'] = $this->factory()->post->create(); // WPCS: global override OK.
+		$output          = '<div></div>';
+		$base_args       = array(
+			'format'      => 'baz',
+			'avatar_size' => 100,
+			'max_depth'   => 5,
+		);
+		$args            = array_merge(
+			$base_args,
+			array(
+				'style' => 'baz',
+			)
+		);
+		$comment         = $this->factory()->comment->create_and_get();
+		$this->walker->start_el( $output, $comment, 0, $args );
+		$this->assertContains( '<li data-sort-time=', $output );
+		$this->assertContains( $comment->comment_ID, $output );
+		$this->assertContains( strval( strtotime( $comment->comment_date ) ), $output );
+
+		$output  = '<div></div>';
+		$args    = array_merge(
+			$base_args,
+			array(
+				'style' => 'div',
+			)
+		);
+		$comment = $this->factory()->comment->create_and_get();
+		$this->walker->start_el( $output, $comment, 0, $args );
+		$this->assertContains( '<div data-sort-time=', $output );
+	}
+
+	/**
+	 * Test AMP_Comment_Walker::paged_walk.
+	 *
+	 * @covers AMP_Comment_Walker::paged_walk()
+	 */
+	public function test_paged_walk() {
+		$GLOBALS['post'] = $this->factory()->post->create(); // WPCS: global override OK.
+		$comments        = $this->get_comments();
+		$args            = array(
+			'format'      => 'div',
+			'style'       => 'baz',
+			'avatar_size' => 100,
+			'max_depth'   => 5,
+		);
+		$output          = $this->walker->paged_walk( $comments, 5, 1, 5, $args );
+
+		foreach ( $comments as $comment ) {
+			$this->assertContains( $comment->comment_author, $output );
+			$this->assertContains( $comment->comment_content, $output );
+		}
+	}
+
+	/**
+	 * Test AMP_Comment_Walker::build_thread_latest_date.
+	 *
+	 * @covers AMP_Comment_Walker::build_thread_latest_date()
+	 */
+	public function test_build_thread_latest_date() {
+		$comments      = $this->get_comments();
+		$reflection    = new ReflectionObject( $this->walker );
+		$tested_method = $reflection->getMethod( 'build_thread_latest_date' );
+		$tested_method->setAccessible( true );
+		$latest_time        = $tested_method->invoke( $this->walker, $comments );
+		$comment_thread_age = $reflection->getProperty( 'comment_thread_age' );
+		$comment_thread_age->setAccessible( true );
+		$comment_thread_value = $comment_thread_age->getValue( $this->walker );
+
+		foreach ( $comments as $comment ) {
+			$this->assertEquals( strtotime( $comment->comment_date ), $comment_thread_value[ $comment->comment_ID ] );
+		}
+
+		$last_comment = end( $comments );
+		$this->assertEquals( strtotime( $last_comment->comment_date ), $latest_time );
+	}
+
+	/**
+	 * Gets comments for tests.
+	 *
+	 * @return array $comments An array of WP_Comment instances.
+	 */
+	public function get_comments() {
+		$comments = array();
+		for ( $i = 0; $i < 5; $i++ ) {
+			$comments[] = $this->factory()->comment->create_and_get( array(
+				'comment_date' => gmdate( 'Y-m-d H:i:s', ( time() + $i ) ), // Ensure each comment has a different date.
+			) );
+		}
+		return $comments;
+	}
+
+}
diff --git a/tests/test-class-amp-comments-sanitizer.php b/tests/test-class-amp-comments-sanitizer.php
new file mode 100644
index 00000000000..d5cfda24882
--- /dev/null
+++ b/tests/test-class-amp-comments-sanitizer.php
@@ -0,0 +1,131 @@
+<?php
+/**
+ * Tests for AMP_Comments_Sanitizer class.
+ *
+ * @package AMP
+ */
+
+/**
+ * Tests for AMP_Comments_Sanitizer class.
+ *
+ * @since 0.7
+ */
+class Test_AMP_Comments_Sanitizer extends WP_UnitTestCase {
+
+	/**
+	 * The tested instance.
+	 *
+	 * @var AMP_Comments_Sanitizer
+	 */
+	public $instance;
+
+	/**
+	 * Representation of the DOM.
+	 *
+	 * @var DOMDocument
+	 */
+	public $dom;
+
+	/**
+	 * Setup.
+	 *
+	 * @inheritdoc
+	 */
+	public function setUp() {
+		parent::setUp();
+		$GLOBALS['post'] = $this->factory()->post->create_and_get(); // WPCS: global override ok.
+		$this->dom       = new DOMDocument();
+		$this->instance  = new AMP_Comments_Sanitizer( $this->dom );
+	}
+
+	/**
+	 * Test AMP_Comments_Sanitizer::sanitize.
+	 *
+	 * @covers AMP_Comments_Sanitizer::sanitize()
+	 */
+	public function test_sanitize() {
+		$form = $this->create_form( 'incorrect-action.php' );
+		$this->instance->sanitize();
+		$on = $form->getAttribute( 'on' );
+		$this->assertNotContains( 'submit:AMP.setState(', $on );
+		$this->assertNotContains( 'submit-error:AMP.setState(', $on );
+		foreach ( $this->get_element_names() as $name ) {
+			$this->assertNotContains( $name, $on );
+		}
+
+		// Use an allowed action.
+		$form = $this->create_form( '/wp-comments-post.php' );
+		$this->instance->sanitize();
+		$on = $form->getAttribute( 'on' );
+		$this->assertContains( 'submit:AMP.setState(', $on );
+		$this->assertContains( 'submit-error:AMP.setState(', $on );
+		foreach ( $this->get_element_names() as $name ) {
+			$this->assertContains( $name, $on );
+		}
+	}
+
+	/**
+	 * Test AMP_Comments_Sanitizer::process_comment_form.
+	 *
+	 * @covers AMP_Comments_Sanitizer::process_comment_form()
+	 */
+	public function test_process_comment_form() {
+		$form          = $this->create_form( '/wp-comments-post.php' );
+		$reflection    = new ReflectionObject( $this->instance );
+		$tested_method = $reflection->getMethod( 'process_comment_form' );
+		$tested_method->setAccessible( true );
+		$tested_method->invoke( $this->instance, $form );
+		$on        = $form->getAttribute( 'on' );
+		$amp_state = $this->dom->getElementsByTagName( 'amp-state' )->item( 0 );
+
+		$this->assertContains( 'submit:AMP.setState(', $on );
+		$this->assertContains( 'submit-error:AMP.setState(', $on );
+		$this->assertContains( 'submit-success:AMP.setState(', $on );
+		$this->assertContains( strval( $GLOBALS['post']->ID ), $on );
+		$this->assertEquals( 'script', $amp_state->firstChild->nodeName );
+
+		foreach ( $this->get_element_names() as $name ) {
+			$this->assertContains( $name, $on );
+			$this->assertContains( $name, $amp_state->nodeValue );
+		}
+		foreach ( $form->getElementsByTagName( 'input' ) as $input ) {
+			$on = $input->getAttribute( 'on' );
+			$this->assertContains( 'change:AMP.setState(', $on );
+			$this->assertContains( strval( $GLOBALS['post']->ID ), $on );
+		}
+	}
+
+	/**
+	 * Creates a form for testing.
+	 *
+	 * @param string $action_value Value of the 'action' attribute.
+	 * @return DomElement $form A form element.
+	 */
+	public function create_form( $action_value ) {
+		$form = $this->dom->createElement( 'form' );
+		$this->dom->appendChild( $form );
+		$form->setAttribute( 'action', $action_value );
+
+		foreach ( $this->get_element_names() as $name ) {
+			$element = $this->dom->createElement( 'input' );
+			$element->setAttribute( 'name', $name );
+			$element->setAttribute( 'value', $GLOBALS['post']->ID );
+			$form->appendChild( $element );
+		}
+		return $form;
+	}
+
+	/**
+	 * Gets the element names to add to the <form>.
+	 *
+	 * @return array An array of strings to add to the <form>.
+	 */
+	public function get_element_names() {
+		return array(
+			'comment_post_ID',
+			'foo',
+			'bar',
+		);
+	}
+
+}
diff --git a/tests/test-class-amp-dom-utils.php b/tests/test-class-amp-dom-utils.php
index 67b0b1aa96c..7fe8106fd07 100644
--- a/tests/test-class-amp-dom-utils.php
+++ b/tests/test-class-amp-dom-utils.php
@@ -145,4 +145,75 @@ public function test_html5_empty_elements() {
 		$this->assertEquals( 'div', $video->childNodes->item( 4 )->nodeName );
 		$this->assertEquals( 'span', $video->childNodes->item( 5 )->nodeName );
 	}
+
+	/**
+	 * Test encoding.
+	 *
+	 * @covers \AMP_DOM_Utils::get_dom()
+	 */
+	public function test_get_dom_encoding() {
+		$html  = '<!DOCTYPE html><html><head><meta charset="utf-8"></head><body>';
+		$html .= '<p>Check out ‘this’ and “that” and—other things.</p>';
+		$html .= '<p>Check out &#8216;this&#8217; and &#8220;that&#8221; and&#8212;other things.</p>';
+		$html .= '<p>Check out &lsquo;this&rsquo; and &ldquo;that&rdquo; and&mdash;other things.</p>';
+		$html .= '</body></html>';
+
+		$document = AMP_DOM_Utils::get_dom_from_content( $html );
+		$this->assertEquals( 'UTF-8', $document->encoding );
+		$paragraphs = $document->getElementsByTagName( 'p' );
+		$this->assertSame( 3, $paragraphs->length );
+		$this->assertSame( $paragraphs->item( 0 )->textContent, $paragraphs->item( 1 )->textContent );
+		$this->assertSame( $paragraphs->item( 1 )->textContent, $paragraphs->item( 2 )->textContent );
+	}
+
+	/**
+	 * Get Table Row Iterations
+	 *
+	 * @return array An array of arrays holding an integer representation of iterations.
+	 */
+	public function get_table_row_iterations() {
+		return array(
+			array( 1 ),
+			array( 10 ),
+			array( 100 ),
+			array( 1000 ),
+		);
+	}
+
+	/**
+	 * Tests attribute conversions on content with iframe srcdocs of variable lengths.
+	 *
+	 * @dataProvider get_table_row_iterations
+	 *
+	 * @param int $iterations The number of table rows to append to iframe srcdoc.
+	 */
+	public function test_attribute_conversion_on_long_iframe_srcdocs( $iterations ) {
+		$html = '<html amp><head><meta charset="utf-8"></head><body><table>';
+
+		for ( $i = 0; $i < $iterations; $i++ ) {
+			$html .= '
+				<tr>
+				<td class="rank" style="width:2%;">1453</td>
+				<td class="text" style="width:10%;">1947</td>
+				<td class="text">Pittsburgh Ironmen</td>
+				<td class="boolean" style="width:10%;text-align:center;"></td>
+				<td class="number" style="width:10%;">1242</td>
+				<td class="number">1192</td>
+				<td class="number">1111</td>
+				<td class="number highlight">1182</td>
+				</tr>
+			';
+		}
+
+		$html .= '</table></body></html>';
+
+		$to_convert = sprintf(
+			'<amp-iframe sandbox="allow-scripts" srcdoc="%s"> </amp-iframe>',
+			htmlentities( $html )
+		);
+
+		AMP_DOM_Utils::convert_amp_bind_attributes( $to_convert );
+
+		$this->assertSame( PREG_NO_ERROR, preg_last_error(), 'Probably failed when backtrack limit was exhausted.' );
+	}
 }
diff --git a/tests/test-class-amp-meta-box.php b/tests/test-class-amp-meta-box.php
index c301a8aaca8..aefba4db352 100644
--- a/tests/test-class-amp-meta-box.php
+++ b/tests/test-class-amp-meta-box.php
@@ -67,6 +67,7 @@ public function test_enqueue_admin_assets() {
 		// Test inline script boot.
 		$this->assertTrue( false !== stripos( wp_json_encode( $script_data ), 'ampPostMetaBox.boot(' ) );
 		unset( $GLOBALS['post'] );
+		unset( $GLOBALS['current_screen'] );
 	}
 
 	/**
@@ -93,13 +94,13 @@ public function test_render_status() {
 		$this->instance->render_status( $post );
 		$this->assertContains( $amp_status_markup, ob_get_clean() );
 
-		remove_post_type_support( 'post', AMP_QUERY_VAR );
+		remove_post_type_support( 'post', amp_get_slug() );
 
 		ob_start();
 		$this->instance->render_status( $post );
 		$this->assertEmpty( ob_get_clean() );
 
-		add_post_type_support( 'post', AMP_QUERY_VAR );
+		add_post_type_support( 'post', amp_get_slug() );
 		wp_set_current_user( $this->factory->user->create( array(
 			'role' => 'subscriber',
 		) ) );
@@ -160,7 +161,7 @@ public function test_preview_post_link() {
 		$link = 'https://foo.bar';
 		$this->assertEquals( 'https://foo.bar', $this->instance->preview_post_link( $link ) );
 		$_POST['amp-preview'] = 'do-preview';
-		$this->assertEquals( 'https://foo.bar?' . AMP_QUERY_VAR . '=1', $this->instance->preview_post_link( $link ) );
+		$this->assertEquals( 'https://foo.bar?' . amp_get_slug() . '=1', $this->instance->preview_post_link( $link ) );
 	}
 
 }
diff --git a/tests/test-class-amp-options-manager.php b/tests/test-class-amp-options-manager.php
index afe0ffc0863..d08584efdd3 100644
--- a/tests/test-class-amp-options-manager.php
+++ b/tests/test-class-amp-options-manager.php
@@ -171,7 +171,7 @@ public function test_check_supported_post_type_update_errors() {
 		$this->assertEmpty( get_settings_errors() );
 
 		// Activation error.
-		remove_post_type_support( 'foo', AMP_QUERY_VAR );
+		remove_post_type_support( 'foo', amp_get_slug() );
 		AMP_Options_Manager::check_supported_post_type_update_errors();
 		$errors = get_settings_errors();
 		$this->assertCount( 1, $errors );
@@ -181,7 +181,7 @@ public function test_check_supported_post_type_update_errors() {
 
 		// Deactivation error.
 		AMP_Options_Manager::update_option( 'supported_post_types', array() );
-		add_post_type_support( 'foo', AMP_QUERY_VAR );
+		add_post_type_support( 'foo', amp_get_slug() );
 		AMP_Options_Manager::check_supported_post_type_update_errors();
 		$errors = get_settings_errors();
 		$this->assertCount( 1, $errors );
diff --git a/tests/test-class-amp-options-menu.php b/tests/test-class-amp-options-menu.php
index ec5109d2612..035706e3b85 100644
--- a/tests/test-class-amp-options-menu.php
+++ b/tests/test-class-amp-options-menu.php
@@ -43,7 +43,7 @@ public function test_constants() {
 	 */
 	public function test_init() {
 		$this->instance->init();
-		$this->assertEquals( 10, has_action( 'admin_menu', array( $this->instance, 'add_menu_items' ) ) );
+		$this->assertEquals( 9, has_action( 'admin_menu', array( $this->instance, 'add_menu_items' ) ) );
 		$this->assertEquals( 10, has_action( 'admin_post_amp_analytics_options', 'AMP_Options_Manager::handle_analytics_submit' ) );
 	}
 
diff --git a/tests/test-class-amp-playlist-embed-handler.php b/tests/test-class-amp-playlist-embed-handler.php
new file mode 100644
index 00000000000..70088396756
--- /dev/null
+++ b/tests/test-class-amp-playlist-embed-handler.php
@@ -0,0 +1,344 @@
+<?php
+/**
+ * Tests for AMP_Playlist_Embed_Handler.
+ *
+ * @package AMP
+ * @since 0.7
+ */
+
+/**
+ * Tests for AMP_Playlist_Embed_Handler.
+ *
+ * @package AMP
+ * @covers AMP_Playlist_Embed_Handler
+ */
+class Test_AMP_Playlist_Embed_Handler extends WP_UnitTestCase {
+
+	/**
+	 * Instance of the tested class.
+	 *
+	 * @var AMP_Playlist_Embed_Handler.
+	 */
+	public $instance;
+
+	/**
+	 * The first tested file.
+	 *
+	 * @var string.
+	 */
+	public $file_1;
+
+	/**
+	 * The second tested file.
+	 *
+	 * @var string.
+	 */
+	public $file_2;
+
+	/**
+	 * Set up test.
+	 */
+	public function setUp() {
+		parent::setUp();
+		$this->instance = new AMP_Playlist_Embed_Handler();
+	}
+
+	/**
+	 * Tear down test.
+	 *
+	 * @global WP_Styles $wp_styles
+	 */
+	public function tearDown() {
+		global $wp_styles;
+		$wp_styles = null;
+
+		AMP_Playlist_Embed_Handler::$playlist_id = 0;
+	}
+
+	/**
+	 * Test register_embed.
+	 *
+	 * @covers AMP_Playlist_Embed_Handler::register_embed()
+	 */
+	public function test_register_embed() {
+		global $shortcode_tags;
+		$removed_shortcode = 'wp_playlist_shortcode';
+		add_shortcode( 'playlist', $removed_shortcode );
+		$this->instance->register_embed();
+		$this->assertEquals( 'AMP_Playlist_Embed_Handler', get_class( $shortcode_tags[ AMP_Playlist_Embed_Handler::SHORTCODE ][0] ) );
+		$this->assertEquals( 'shortcode', $shortcode_tags[ AMP_Playlist_Embed_Handler::SHORTCODE ][1] );
+		$this->assertEquals( $removed_shortcode, $this->instance->removed_shortcode_callback );
+		$this->instance->unregister_embed();
+	}
+
+	/**
+	 * Test unregister_embed.
+	 *
+	 * @covers AMP_Playlist_Embed_Handler::unregister_embed()
+	 */
+	public function test_unregister_embed() {
+		global $shortcode_tags;
+		$expected_removed_shortcode                 = 'wp_playlist_shortcode';
+		$this->instance->removed_shortcode_callback = $expected_removed_shortcode;
+		$this->instance->unregister_embed();
+		$this->assertEquals( $expected_removed_shortcode, $shortcode_tags[ AMP_Playlist_Embed_Handler::SHORTCODE ] );
+	}
+
+	/**
+	 * Test styling.
+	 *
+	 * @covers AMP_Playlist_Embed_Handler::enqueue_styles()
+	 */
+	public function test_styling() {
+		global $post;
+		$playlist_shortcode = 'amp-playlist-shortcode';
+		$this->instance->register_embed();
+		$this->assertFalse( in_array( 'wp-mediaelement', wp_styles()->queue, true ) );
+		$this->assertFalse( in_array( $playlist_shortcode, wp_styles()->queue, true ) );
+
+		$post               = $this->factory()->post->create_and_get(); // WPCS: global override OK.
+		$post->post_content = '[playlist ids="5,3"]';
+		$this->instance->enqueue_styles();
+		$style = wp_styles()->registered[ $playlist_shortcode ];
+		$this->assertContains( $playlist_shortcode, wp_styles()->queue );
+		$this->assertEquals( array( 'wp-mediaelement' ), $style->deps );
+		$this->assertEquals( $playlist_shortcode, $style->handle );
+		$this->assertEquals( amp_get_asset_url( 'css/amp-playlist-shortcode.css' ), $style->src );
+		$this->assertEquals( AMP__VERSION, $style->ver );
+	}
+
+	/**
+	 * Test shortcode.
+	 *
+	 * @covers AMP_Playlist_Embed_Handler::shortcode()
+	 * @covers AMP_Playlist_Embed_Handler::video_playlist()
+	 */
+	public function test_shortcode() {
+		$attr     = $this->get_attributes( 'video' );
+		$playlist = $this->instance->shortcode( $attr );
+		$this->assertContains( '<amp-video', $playlist );
+		$this->assertContains( '<amp-state', $playlist );
+		$this->assertContains( $this->file_1, $playlist );
+		$this->assertContains( $this->file_2, $playlist );
+	}
+
+	/**
+	 * Test video_playlist.
+	 *
+	 * @covers AMP_Playlist_Embed_Handler::video_playlist()
+	 */
+	public function test_video_playlist() {
+		$attr     = $this->get_attributes( 'video' );
+		$data     = $this->instance->get_data( $attr );
+		$playlist = $this->instance->video_playlist( $data );
+		$this->assertContains( '<amp-video', $playlist );
+		$this->assertContains( '<amp-state', $playlist );
+		$this->assertContains( $this->file_1, $playlist );
+		$this->assertContains( $this->file_2, $playlist );
+		$this->assertContains( '[src]="wpPlaylist1[wpPlaylist1.selectedIndex].videoUrl"', $playlist );
+		$this->assertContains( 'on="tap:AMP.setState({&quot;wpPlaylist1&quot;:{&quot;selectedIndex&quot;:0}})"', $playlist );
+	}
+
+	/**
+	 * Test get_thumb_dimensions.
+	 *
+	 * @covers AMP_Playlist_Embed_Handler::get_thumb_dimensions()
+	 */
+	public function test_get_thumb_dimensions() {
+		$dimensions = array(
+			'height' => 60,
+			'width'  => 60,
+		);
+		$track      = array(
+			'thumb' => $dimensions,
+		);
+		$this->assertEquals( $dimensions, $this->instance->get_thumb_dimensions( $track ) );
+
+		$dimensions = array(
+			'height' => 68,
+			'width'  => 59,
+		);
+		$track      = array(
+			'thumb' => $dimensions,
+		);
+		$this->assertEquals( $dimensions, $this->instance->get_thumb_dimensions( $track ) );
+
+		$dimensions          = array(
+			'height' => 70,
+			'width'  => 80.5,
+		);
+		$expected_dimensions = array(
+			'height' => 52,
+			'width'  => 60,
+		);
+		$track               = array(
+			'thumb' => $dimensions,
+		);
+		$this->assertEquals( $expected_dimensions, $this->instance->get_thumb_dimensions( $track ) );
+
+		$dimensions          = array(
+			'width' => 80.5,
+		);
+		$track               = array(
+			'thumb' => $dimensions,
+		);
+		$expected_dimensions = array(
+			'height' => 48,
+			'width'  => 60,
+		);
+		$this->assertEquals( $expected_dimensions, $this->instance->get_thumb_dimensions( $track ) );
+
+		$track               = array(
+			'thumb' => array(),
+		);
+		$expected_dimensions = array(
+			'height' => AMP_Playlist_Embed_Handler::DEFAULT_THUMB_HEIGHT,
+			'width'  => AMP_Playlist_Embed_Handler::DEFAULT_THUMB_WIDTH,
+		);
+		$this->assertEquals( $expected_dimensions, $this->instance->get_thumb_dimensions( $track ) );
+	}
+
+	/**
+	 * Test audio_playlist.
+	 *
+	 * Logic for creating the videos copied from Tests_Media.
+	 *
+	 * @covers AMP_Playlist_Embed_Handler::audio_playlist()
+	 */
+	public function test_audio_playlist() {
+		$attr     = $this->get_attributes( 'audio' );
+		$playlist = $this->instance->audio_playlist( array() );
+		$this->assertEquals( '', $playlist );
+
+		$data     = $this->instance->get_data( $attr );
+		$playlist = $this->instance->audio_playlist( $data );
+		$this->assertContains( '<amp-carousel', $playlist );
+		$this->assertContains( '<amp-audio', $playlist );
+		$this->assertContains( $this->file_1, $playlist );
+		$this->assertContains( $this->file_2, $playlist );
+		$this->assertContains( 'tap:AMP.setState({&quot;wpPlaylist1&quot;:{&quot;selectedIndex&quot;:0}})"', $playlist );
+	}
+
+	/**
+	 * Test tracks.
+	 *
+	 * @covers AMP_Playlist_Embed_Handler::print_tracks()
+	 */
+	public function test_tracks() {
+		$type         = 'video';
+		$attr         = $this->get_attributes( $type );
+		$data         = $this->instance->get_data( $attr );
+		$container_id = 'fooContainerId1';
+		$state_id     = 'fooId1';
+		$expected_on  = 'tap:AMP.setState({&quot;' . $state_id . '&quot;:{&quot;selectedIndex&quot;:0}})';
+
+		ob_start();
+		$this->instance->print_tracks( $state_id, $data['tracks'] );
+		$tracks = ob_get_clean();
+		$this->assertContains( '<div class="wp-playlist-tracks">', $tracks );
+		$this->assertContains( $state_id, $tracks );
+		$this->assertContains( $expected_on, $tracks );
+
+		$attr        = $this->get_attributes( $type );
+		$data        = $this->instance->get_data( $attr );
+		$expected_on = 'tap:AMP.setState({&quot;' . $state_id . '&quot;:{&quot;selectedIndex&quot;:0}})';
+
+		ob_start();
+		$this->instance->print_tracks( $state_id, $data['tracks'] );
+		$tracks = ob_get_clean();
+		$this->assertContains( $expected_on, $tracks );
+	}
+
+	/**
+	 * Test get_data.
+	 *
+	 * @covers AMP_Playlist_Embed_Handler::get_data()
+	 */
+	public function test_get_data() {
+		$type = 'audio';
+		$data = $this->instance->get_data( $this->get_attributes( $type ) );
+		$this->assertEquals( $type, $data['type'] );
+		$this->assertContains( $this->file_1, $data['tracks'][0]['src'] );
+		$this->assertContains( $this->file_2, $data['tracks'][1]['src'] );
+	}
+
+	/**
+	 * Test get_title.
+	 *
+	 * @covers AMP_Playlist_Embed_Handler::get_data()
+	 */
+	public function test_get_title() {
+		$caption = 'Example caption';
+		$title   = 'Media Title';
+		$track   = array(
+			'caption' => $caption,
+		);
+
+		$this->assertEquals( $caption, $this->instance->get_title( $track ) );
+
+		$track = array(
+			'title' => $title,
+		);
+		$this->assertEquals( $title, $this->instance->get_title( $track ) );
+
+		$track = array(
+			'caption' => $caption,
+			'title'   => $title,
+		);
+		$this->assertEquals( $caption, $this->instance->get_title( $track ) );
+		$this->assertEquals( null, $this->instance->get_title( array() ) );
+	}
+
+	/**
+	 * Gets the shortcode attributes.
+	 *
+	 * @param string $type The type of shortcode attributes: 'audio' or 'video'.
+	 * @return array $attrs The shortcode attributes.
+	 */
+	public function get_attributes( $type ) {
+		if ( 'audio' === $type ) {
+			$this->file_1 = 'example-audio-1.mp3';
+			$this->file_2 = 'example-audio-2.mp3';
+			$mime_type    = 'audio/mp3';
+		} elseif ( 'video' === $type ) {
+			$this->file_1 = 'example-video-1.mp4';
+			$this->file_2 = 'example-video-2.mkv';
+			$mime_type    = 'video/mp4';
+		} else {
+			return;
+		}
+
+		$files = array(
+			$this->file_1,
+			$this->file_2,
+		);
+		$ids   = $this->get_file_ids( $files, $mime_type );
+		return array(
+			'ids'  => implode( ',', $ids ),
+			'type' => $type,
+		);
+	}
+
+	/**
+	 * Gets test file IDs.
+	 *
+	 * @param array  $files     The file names to create.
+	 * @param string $mime_type The type of file.
+	 * @return array $ids The IDs of the test files.
+	 */
+	public function get_file_ids( $files, $mime_type ) {
+		$ids = array();
+		foreach ( $files as $file ) {
+			$ids[] = $this->factory()->attachment->create_object(
+				$file,
+				0,
+				array(
+					'post_mime_type' => $mime_type,
+					'post_type'      => 'attachment',
+				)
+			);
+		}
+		return $ids;
+	}
+
+}
diff --git a/tests/test-class-amp-post-type-support.php b/tests/test-class-amp-post-type-support.php
index 733d9ae46c2..b32674715d4 100644
--- a/tests/test-class-amp-post-type-support.php
+++ b/tests/test-class-amp-post-type-support.php
@@ -73,9 +73,9 @@ public function test_add_post_type_support() {
 		AMP_Options_Manager::update_option( 'supported_post_types', array( 'poem' ) );
 
 		AMP_Post_Type_Support::add_post_type_support();
-		$this->assertTrue( post_type_supports( 'post', AMP_QUERY_VAR ) );
-		$this->assertTrue( post_type_supports( 'poem', AMP_QUERY_VAR ) );
-		$this->assertFalse( post_type_supports( 'book', AMP_QUERY_VAR ) );
+		$this->assertTrue( post_type_supports( 'post', amp_get_slug() ) );
+		$this->assertTrue( post_type_supports( 'poem', amp_get_slug() ) );
+		$this->assertFalse( post_type_supports( 'book', amp_get_slug() ) );
 	}
 
 	/**
@@ -92,7 +92,7 @@ public function test_get_support_error() {
 		// Post type support.
 		$book_id = $this->factory()->post->create( array( 'post_type' => 'book' ) );
 		$this->assertEquals( array( 'post-type-support' ), AMP_Post_Type_Support::get_support_errors( $book_id ) );
-		add_post_type_support( 'book', AMP_QUERY_VAR );
+		add_post_type_support( 'book', amp_get_slug() );
 		$this->assertEmpty( AMP_Post_Type_Support::get_support_errors( $book_id ) );
 
 		// Password-protected.
diff --git a/tests/test-class-amp-theme-support.php b/tests/test-class-amp-theme-support.php
index b71c4d41228..df6e94b0301 100644
--- a/tests/test-class-amp-theme-support.php
+++ b/tests/test-class-amp-theme-support.php
@@ -13,14 +13,123 @@
  */
 class Test_AMP_Theme_Support extends WP_UnitTestCase {
 
+	/**
+	 * The name of the tested class.
+	 *
+	 * @var string
+	 */
+	const TESTED_CLASS = 'AMP_Theme_Support';
+
 	/**
 	 * After a test method runs, reset any state in WordPress the test method might have changed.
+	 *
+	 * @global WP_Scripts $wp_scripts
 	 */
 	public function tearDown() {
+		global $wp_scripts;
+		$wp_scripts = null;
 		parent::tearDown();
 		remove_theme_support( 'amp' );
 		$_REQUEST                = array(); // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
 		$_SERVER['QUERY_STRING'] = '';
+		unset( $_SERVER['REQUEST_URI'] );
+		unset( $_SERVER['REQUEST_METHOD'] );
+		if ( isset( $GLOBALS['wp_customize'] ) ) {
+			$GLOBALS['wp_customize']->stop_previewing_theme();
+		}
+		AMP_Theme_Support::$headers_sent = array();
+	}
+
+	/**
+	 * Test init.
+	 *
+	 * @covers AMP_Theme_Support::init()
+	 * @covers AMP_Theme_Support::finish_init()
+	 */
+	public function test_init() {
+		$_REQUEST['__amp_source_origin'] = 'foo';
+		$_GET['__amp_source_origin']     = 'foo';
+		AMP_Theme_Support::init();
+		$this->assertNotEquals( 10, has_action( 'widgets_init', array( self::TESTED_CLASS, 'register_widgets' ) ) );
+
+		// Ensure that purge_amp_query_vars() didn't execute.
+		$this->assertTrue( isset( $_REQUEST['__amp_source_origin'] ) ); // WPCS: CSRF ok.
+
+		add_theme_support( 'amp' );
+		AMP_Theme_Support::init();
+		$this->assertEquals( 10, has_action( 'widgets_init', array( self::TESTED_CLASS, 'register_widgets' ) ) );
+		$this->assertEquals( PHP_INT_MAX, has_action( 'wp', array( self::TESTED_CLASS, 'finish_init' ) ) );
+		$this->assertFalse( isset( $_REQUEST['__amp_source_origin'] ) ); // WPCS: CSRF ok.
+
+		add_theme_support( 'amp', 'invalid_argumnet_type' );
+		$e = null;
+		try {
+			AMP_Theme_Support::init();
+		} catch ( Exception $exception ) {
+			$e = $exception;
+		}
+		$this->assertInstanceOf( 'PHPUnit_Framework_Error_Notice', $e );
+		$this->assertEquals( 'Expected AMP theme support arg to be array.', $e->getMessage() );
+
+		add_theme_support( 'amp', array(
+			'invalid_param_key' => array(),
+		) );
+		try {
+			AMP_Theme_Support::init();
+		} catch ( Exception $exception ) {
+			$e = $exception;
+		}
+		$this->assertEquals( 'Expected AMP theme support to only have template_dir and/or available_callback.', $e->getMessage() );
+	}
+
+	/**
+	 * Test that amphtml link is added at the right time.
+	 *
+	 * @covers AMP_Theme_Support::finish_init()
+	 */
+	public function test_amphtml_link() {
+		$post_id = $this->factory()->post->create( array( 'post_title' => 'Test' ) );
+		add_theme_support( 'amp', array(
+			'template_dir'       => '...',
+			'available_callback' => function() {
+				return is_singular();
+			},
+		) );
+
+		// Test paired mode singular.
+		remove_action( 'wp_head', 'amp_frontend_add_canonical' );
+		$this->go_to( get_permalink( $post_id ) );
+		AMP_Theme_Support::finish_init();
+		$this->assertEquals( 10, has_action( 'wp_head', 'amp_frontend_add_canonical' ) );
+
+		// Test paired mode homepage.
+		remove_action( 'wp_head', 'amp_frontend_add_canonical' );
+		$this->go_to( home_url() );
+		AMP_Theme_Support::finish_init();
+		$this->assertFalse( has_action( 'wp_head', 'amp_frontend_add_canonical' ) );
+
+		// Test canonical.
+		remove_theme_support( 'amp' );
+		add_theme_support( 'amp' );
+		$this->go_to( get_permalink( $post_id ) );
+		AMP_Theme_Support::finish_init();
+		$this->assertFalse( has_action( 'wp_head', 'amp_frontend_add_canonical' ) );
+	}
+
+	/**
+	 * Test redirect_canonical_amp.
+	 *
+	 * @covers AMP_Theme_Support::redirect_canonical_amp()
+	 */
+	public function test_redirect_canonical_amp() {
+		set_query_var( amp_get_slug(), 1 );
+		try {
+			AMP_Theme_Support::redirect_canonical_amp();
+		} catch ( Exception $exception ) {
+			$e = $exception;
+		}
+		// wp_safe_redirect() modifies the headers, and causes an error.
+		$this->assertTrue( isset( $e ) );
 	}
 
 	/**
@@ -70,6 +179,411 @@ public function test_is_paired_available() {
 		$this->assertFalse( AMP_Theme_Support::is_paired_available() );
 	}
 
+	/**
+	 * Test is_customize_preview_iframe.
+	 *
+	 * @covers AMP_Theme_Support::is_customize_preview_iframe()
+	 */
+	public function test_is_customize_preview_iframe() {
+		require_once ABSPATH . WPINC . '/class-wp-customize-manager.php';
+		$GLOBALS['wp_customize'] = new WP_Customize_Manager();
+		$this->assertFalse( AMP_Theme_Support::is_customize_preview_iframe() );
+		$GLOBALS['wp_customize'] = new WP_Customize_Manager( array(
+			'messenger_channel' => 'baz',
+		) );
+		$this->assertFalse( AMP_Theme_Support::is_customize_preview_iframe() );
+		$GLOBALS['wp_customize']->start_previewing_theme();
+		$this->assertTrue( AMP_Theme_Support::is_customize_preview_iframe() );
+	}
+
+	/**
+	 * Test register_paired_hooks.
+	 *
+	 * @covers AMP_Theme_Support::register_paired_hooks()
+	 */
+	public function test_register_paired_hooks() {
+		$template_types = array(
+			'paged',
+			'index',
+			'404',
+			'archive',
+			'author',
+			'category',
+		);
+		AMP_Theme_Support::register_paired_hooks();
+		foreach ( $template_types as $template_type ) {
+			$this->assertEquals( 10, has_filter( "{$template_type}_template_hierarchy", array( self::TESTED_CLASS, 'filter_paired_template_hierarchy' ) ) );
+		}
+		$this->assertEquals( 100, has_filter( 'template_include', array( self::TESTED_CLASS, 'filter_paired_template_include' ) ) );
+	}
+
+	/**
+	 * Test validate_non_amp_theme.
+	 *
+	 * @global WP_Widget_Factory $wp_widget_factory
+	 * @global WP_Scripts $wp_scripts
+	 * @covers AMP_Theme_Support::prepare_response()
+	 */
+	public function test_validate_non_amp_theme() {
+		add_theme_support( 'amp' );
+		AMP_Theme_Support::init();
+		AMP_Theme_Support::finish_init();
+
+		ob_start();
+		?>
+		<!DOCTYPE html>
+		<html lang="en-US" class="no-js">
+			<head>
+				<meta charset="UTF-8">
+				<meta name="viewport" content="width=device-width">
+				<?php wp_head(); ?>
+			</head>
+			<body>
+				<?php wp_print_scripts( 'amp-mathml' ); ?>
+			</body>
+		</html>
+		<?php
+		$original_html  = trim( ob_get_clean() );
+		$sanitized_html = AMP_Theme_Support::prepare_response( $original_html );
+
+		// Invalid viewport meta tag is not present.
+		$this->assertNotContains( '<meta name="viewport" content="width=device-width">', $sanitized_html );
+
+		// Correct viewport meta tag was added.
+		$this->assertContains( '<meta name="viewport" content="width=device-width,minimum-scale=1">', $sanitized_html );
+
+		// MathML script was added.
+		$this->assertContains( '<script type="text/javascript" src="https://cdn.ampproject.org/v0/amp-mathml-latest.js" async custom-element="amp-mathml"></script>', $sanitized_html ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
+	}
+
+	/**
+	 * Test add_hooks.
+	 *
+	 * @covers AMP_Theme_Support::add_hooks()
+	 */
+	public function test_add_hooks() {
+		AMP_Theme_Support::add_hooks();
+		$this->assertFalse( has_action( 'wp_head', 'wp_post_preview_js' ) );
+		$this->assertFalse( has_action( 'wp_head', 'print_emoji_detection_script' ) );
+		$this->assertFalse( has_action( 'wp_print_styles', 'print_emoji_styles' ) );
+		$this->assertFalse( has_action( 'wp_head', 'wp_oembed_add_host_js' ) );
+
+		$this->assertEquals( 0, has_action( 'wp_print_styles', array( self::TESTED_CLASS, 'print_amp_styles' ) ) );
+		$this->assertEquals( 20, has_action( 'wp_head', 'amp_add_generator_metadata' ) );
+		$this->assertEquals( 20, has_action( 'wp_head', 'amp_add_generator_metadata' ) );
+		$this->assertEquals( 10, has_action( 'wp_enqueue_scripts', array( self::TESTED_CLASS, 'enqueue_assets' ) ) );
+
+		$this->assertEquals( 1000, has_action( 'wp_enqueue_scripts', array( self::TESTED_CLASS, 'dequeue_customize_preview_scripts' ) ) );
+		$this->assertEquals( 10, has_filter( 'customize_partial_render', array( self::TESTED_CLASS, 'filter_customize_partial_render' ) ) );
+		$this->assertEquals( 10, has_action( 'wp_footer', 'amp_print_analytics' ) );
+		$this->assertEquals( 100, has_filter( 'show_admin_bar', '__return_false' ) );
+		$this->assertEquals( 0, has_action( 'template_redirect', array( self::TESTED_CLASS, 'start_output_buffering' ) ) );
+
+		$this->assertEquals( PHP_INT_MAX, has_filter( 'wp_list_comments_args', array( self::TESTED_CLASS, 'set_comments_walker' ) ) );
+		$this->assertEquals( 10, has_filter( 'comment_form_defaults', array( self::TESTED_CLASS, 'filter_comment_form_defaults' ) ) );
+		$this->assertEquals( 10, has_filter( 'comment_reply_link', array( self::TESTED_CLASS, 'filter_comment_reply_link' ) ) );
+		$this->assertEquals( 10, has_filter( 'cancel_comment_reply_link', array( self::TESTED_CLASS, 'filter_cancel_comment_reply_link' ) ) );
+		$this->assertEquals( 100, has_action( 'comment_form', array( self::TESTED_CLASS, 'amend_comment_form' ) ) );
+		$this->assertFalse( has_action( 'comment_form', 'wp_comment_form_unfiltered_html_nonce' ) );
+	}
+
+	/**
+	 * Test purge_amp_query_vars.
+	 *
+	 * @covers AMP_Theme_Support::purge_amp_query_vars()
+	 */
+	public function test_purge_amp_query_vars() {
+		// phpcs:disable WordPress.CSRF.NonceVerification.NoNonceVerification
+		$bad_query_vars = array(
+			'amp_latest_update_time' => '1517199956',
+			'amp_last_check_time'    => '1517599126',
+			'__amp_source_origin'    => home_url(),
+		);
+		$ok_query_vars  = array(
+			'bar' => 'baz',
+		);
+		$all_query_vars = array_merge( $bad_query_vars, $ok_query_vars );
+
+		$_SERVER['QUERY_STRING'] = build_query( $all_query_vars );
+
+		remove_action( 'wp', 'amp_maybe_add_actions' );
+		$this->go_to( add_query_arg( $all_query_vars, home_url( '/foo/' ) ) );
+		$_REQUEST = $_GET;
+		foreach ( $all_query_vars as $key => $value ) {
+			$this->assertArrayHasKey( $key, $_GET );
+			$this->assertArrayHasKey( $key, $_REQUEST );
+			$this->assertContains( "$key=$value", $_SERVER['QUERY_STRING'] );
+			$this->assertContains( "$key=$value", $_SERVER['REQUEST_URI'] );
+		}
+
+		AMP_Theme_Support::$purged_amp_query_vars = array();
+		AMP_Theme_Support::purge_amp_query_vars();
+		$this->assertEqualSets( AMP_Theme_Support::$purged_amp_query_vars, $bad_query_vars );
+
+		foreach ( $bad_query_vars as $key => $value ) {
+			$this->assertArrayNotHasKey( $key, $_GET );
+			$this->assertArrayNotHasKey( $key, $_REQUEST );
+			$this->assertNotContains( "$key=$value", $_SERVER['QUERY_STRING'] );
+			$this->assertNotContains( "$key=$value", $_SERVER['REQUEST_URI'] );
+		}
+		foreach ( $ok_query_vars as $key => $value ) {
+			$this->assertArrayHasKey( $key, $_GET );
+			$this->assertArrayHasKey( $key, $_REQUEST );
+			$this->assertContains( "$key=$value", $_SERVER['QUERY_STRING'] );
+			$this->assertContains( "$key=$value", $_SERVER['REQUEST_URI'] );
+		}
+		// phpcs:enable WordPress.CSRF.NonceVerification.NoNonceVerification
+	}
+
+	/**
+	 * Test send_header.
+	 *
+	 * @covers AMP_Theme_Support::send_header()
+	 */
+	public function test_send_header() {
+		$name         = 'foo';
+		$value        = 'bar';
+		$args         = array(
+			'X-Example' => 'baz',
+		);
+		$default_args = array(
+			'replace'     => true,
+			'status_code' => null,
+		);
+		AMP_Theme_Support::send_header( $name, $value, $args );
+		$this->assertEquals( array_merge( compact( 'name', 'value' ), $args, $default_args ), reset( AMP_Theme_Support::$headers_sent ) );
+	}
+
+	/**
+	 * Test handle_xhr_request().
+	 *
+	 * @covers AMP_Theme_Support::handle_xhr_request()
+	 */
+	public function test_handle_xhr_request() {
+		AMP_Theme_Support::purge_amp_query_vars();
+		AMP_Theme_Support::handle_xhr_request();
+		$this->assertEmpty( AMP_Theme_Support::$headers_sent );
+
+		$_GET['_wp_amp_action_xhr_converted'] = '1';
+
+		// Try bad source origin.
+		$_GET['__amp_source_origin'] = 'http://evil.example.com/';
+		$_SERVER['REQUEST_METHOD']   = 'POST';
+		AMP_Theme_Support::purge_amp_query_vars();
+		AMP_Theme_Support::handle_xhr_request();
+		$this->assertEmpty( AMP_Theme_Support::$headers_sent );
+
+		// Try home source origin.
+		$_GET['__amp_source_origin'] = home_url();
+		$_SERVER['REQUEST_METHOD']   = 'POST';
+		AMP_Theme_Support::purge_amp_query_vars();
+		AMP_Theme_Support::handle_xhr_request();
+		$this->assertCount( 1, AMP_Theme_Support::$headers_sent );
+		$this->assertEquals(
+			array(
+				'name'        => 'AMP-Access-Control-Allow-Source-Origin',
+				'value'       => home_url(),
+				'replace'     => true,
+				'status_code' => null,
+			),
+			AMP_Theme_Support::$headers_sent[0]
+		);
+		$this->assertEquals( PHP_INT_MAX, has_filter( 'wp_redirect', array( 'AMP_Theme_Support', 'intercept_post_request_redirect' ) ) );
+		$this->assertEquals( PHP_INT_MAX, has_filter( 'comment_post_redirect', array( 'AMP_Theme_Support', 'filter_comment_post_redirect' ) ) );
+		$this->assertEquals(
+			array( 'AMP_Theme_Support', 'handle_wp_die' ),
+			apply_filters( 'wp_die_handler', '__return_true' )
+		);
+	}
+
+	/**
+	 * Test filter_comment_post_redirect().
+	 *
+	 * @covers AMP_Theme_Support::filter_comment_post_redirect()
+	 */
+	public function test_filter_comment_post_redirect() {
+		add_filter( 'wp_doing_ajax', '__return_true' );
+		add_filter( 'wp_die_ajax_handler', function() {
+			return '__return_null';
+		} );
+
+		add_theme_support( 'amp' );
+		$post    = $this->factory()->post->create_and_get();
+		$comment = $this->factory()->comment->create_and_get( array(
+			'comment_post_ID' => $post->ID,
+		) );
+		$url     = get_comment_link( $comment );
+
+		// Test without comments_live_list.
+		$filtered_url = AMP_Theme_Support::filter_comment_post_redirect( $url, $comment );
+		$this->assertNotEquals(
+			strtok( $url, '#' ),
+			strtok( $filtered_url, '#' )
+		);
+
+		// Test with comments_live_list.
+		add_theme_support( 'amp', array(
+			'comments_live_list' => true,
+		) );
+		add_filter( 'amp_comment_posted_message', function( $message, WP_Comment $filter_comment ) {
+			return sprintf( '(comment=%d,approved=%d)', $filter_comment->comment_ID, $filter_comment->comment_approved );
+		}, 10, 2 );
+
+		// Test approved comment.
+		$comment->comment_approved = '1';
+		ob_start();
+		AMP_Theme_Support::filter_comment_post_redirect( $url, $comment );
+		$response = json_decode( ob_get_clean(), true );
+		$this->assertArrayHasKey( 'message', $response );
+		$this->assertEquals(
+			sprintf( '(comment=%d,approved=1)', $comment->comment_ID ),
+			$response['message']
+		);
+
+		// Test moderated comment.
+		$comment->comment_approved = '0';
+		ob_start();
+		AMP_Theme_Support::filter_comment_post_redirect( $url, $comment );
+		$response = json_decode( ob_get_clean(), true );
+		$this->assertArrayHasKey( 'message', $response );
+		$this->assertEquals(
+			sprintf( '(comment=%d,approved=0)', $comment->comment_ID ),
+			$response['message']
+		);
+	}
+
+	/**
+	 * Test handle_wp_die().
+	 *
+	 * @covers AMP_Theme_Support::handle_wp_die()
+	 */
+	public function test_handle_wp_die() {
+		add_filter( 'wp_doing_ajax', '__return_true' );
+		add_filter( 'wp_die_ajax_handler', function() {
+			return '__return_null';
+		} );
+
+		ob_start();
+		AMP_Theme_Support::handle_wp_die( 'string' );
+		$this->assertEquals( '{"error":"string"}', ob_get_clean() );
+
+		ob_start();
+		$error = new WP_Error( 'code', 'The Message' );
+		AMP_Theme_Support::handle_wp_die( $error );
+		$this->assertEquals( '{"error":"The Message"}', ob_get_clean() );
+	}
+
+	/**
+	 * Test intercept_post_request_redirect().
+	 *
+	 * @covers AMP_Theme_Support::intercept_post_request_redirect()
+	 */
+	public function test_intercept_post_request_redirect() {
+
+		add_theme_support( 'amp' );
+		$url = home_url( '', 'https' ) . ':443/?test=true#test';
+
+		add_filter( 'wp_doing_ajax', '__return_true' );
+		add_filter( 'wp_die_ajax_handler', function () {
+			return '__return_false';
+		} );
+
+		// Test redirecting to full URL with HTTPS protocol.
+		AMP_Theme_Support::$headers_sent = array();
+		ob_start();
+		AMP_Theme_Support::intercept_post_request_redirect( $url );
+		$this->assertEquals( '{"success":true}', ob_get_clean() );
+		$this->assertContains(
+			array(
+				'name'        => 'AMP-Redirect-To',
+				'value'       => $url,
+				'replace'     => true,
+				'status_code' => null,
+			),
+			AMP_Theme_Support::$headers_sent
+		);
+		$this->assertContains(
+			array(
+				'name'        => 'Access-Control-Expose-Headers',
+				'value'       => 'AMP-Redirect-To',
+				'replace'     => true,
+				'status_code' => null,
+			),
+			AMP_Theme_Support::$headers_sent
+		);
+
+		// Test redirecting to non-HTTPS URL.
+		AMP_Theme_Support::$headers_sent = array();
+		ob_start();
+		$url = home_url( '/', 'http' );
+		AMP_Theme_Support::intercept_post_request_redirect( $url );
+		$this->assertEquals( '{"success":true}', ob_get_clean() );
+		$this->assertContains(
+			array(
+				'name'        => 'AMP-Redirect-To',
+				'value'       => preg_replace( '#^\w+:#', '', $url ),
+				'replace'     => true,
+				'status_code' => null,
+			),
+			AMP_Theme_Support::$headers_sent
+		);
+		$this->assertContains(
+			array(
+				'name'        => 'Access-Control-Expose-Headers',
+				'value'       => 'AMP-Redirect-To',
+				'replace'     => true,
+				'status_code' => null,
+			),
+			AMP_Theme_Support::$headers_sent
+		);
+
+		// Test redirecting to host-less location.
+		AMP_Theme_Support::$headers_sent = array();
+		ob_start();
+		AMP_Theme_Support::intercept_post_request_redirect( '/new-location/' );
+		$this->assertEquals( '{"success":true}', ob_get_clean() );
+		$this->assertContains(
+			array(
+				'name'        => 'AMP-Redirect-To',
+				'value'       => set_url_scheme( home_url( '/new-location/' ), 'https' ),
+				'replace'     => true,
+				'status_code' => null,
+			),
+			AMP_Theme_Support::$headers_sent
+		);
+
+		// Test redirecting to scheme-less location.
+		AMP_Theme_Support::$headers_sent = array();
+		ob_start();
+		$url = home_url( '/new-location/' );
+		AMP_Theme_Support::intercept_post_request_redirect( substr( $url, strpos( $url, ':' ) + 1 ) );
+		$this->assertEquals( '{"success":true}', ob_get_clean() );
+		$this->assertContains(
+			array(
+				'name'        => 'AMP-Redirect-To',
+				'value'       => set_url_scheme( home_url( '/new-location/' ), 'https' ),
+				'replace'     => true,
+				'status_code' => null,
+			),
+			AMP_Theme_Support::$headers_sent
+		);
+
+		// Test redirecting to empty location.
+		AMP_Theme_Support::$headers_sent = array();
+		ob_start();
+		AMP_Theme_Support::intercept_post_request_redirect( '' );
+		$this->assertEquals( '{"success":true}', ob_get_clean() );
+		$this->assertContains(
+			array(
+				'name'        => 'AMP-Redirect-To',
+				'value'       => set_url_scheme( home_url(), 'https' ),
+				'replace'     => true,
+				'status_code' => null,
+			),
+			AMP_Theme_Support::$headers_sent
+		);
+	}
+
 	/**
 	 * Test register_widgets().
 	 *
@@ -87,21 +601,401 @@ public function test_register_widgets() {
 		$this->assertArrayHasKey( 'AMP_Widget_Categories', $wp_widget_factory->widgets );
 	}
 
+	/**
+	 * Test register_content_embed_handlers.
+	 *
+	 * @covers AMP_Theme_Support::register_content_embed_handlers()
+	 */
+	public function test_register_content_embed_handlers() {
+		$embed_handlers = AMP_Theme_Support::register_content_embed_handlers();
+		foreach ( $embed_handlers as $embed_handler ) {
+			$this->assertTrue( is_subclass_of( $embed_handler, 'AMP_Base_Embed_Handler' ) );
+			$reflection = new ReflectionObject( $embed_handler );
+			$args       = $reflection->getProperty( 'args' );
+			$args->setAccessible( true );
+			$property = $args->getValue( $embed_handler );
+			$this->assertEquals( AMP_Post_Template::CONTENT_MAX_WIDTH, $property['content_max_width'] );
+		}
+	}
+
+	/**
+	 * Test set_comments_walker.
+	 *
+	 * @covers AMP_Theme_Support::set_comments_walker()
+	 */
+	public function test_set_comments_walker() {
+		$args = AMP_Theme_Support::set_comments_walker( array(
+			'walker' => null,
+		) );
+		$this->assertInstanceOf( 'AMP_Comment_Walker', $args['walker'] );
+	}
+
+	/**
+	 * Test amend_comment_form().
+	 *
+	 * @covers AMP_Theme_Support::amend_comment_form()
+	 */
+	public function test_amend_comment_form() {
+		$post_id = $this->factory()->post->create();
+		$this->go_to( get_permalink( $post_id ) );
+		$this->assertTrue( is_singular() );
+
+		// Test native AMP.
+		add_theme_support( 'amp' );
+		$this->assertTrue( amp_is_canonical() );
+		ob_start();
+		AMP_Theme_Support::amend_comment_form();
+		$output = ob_get_clean();
+		$this->assertNotContains( '<input type="hidden" name="redirect_to"', $output );
+		$this->assertContains( '<div submit-success>', $output );
+		$this->assertContains( '<div submit-error>', $output );
+
+		// Test paired AMP.
+		add_theme_support( 'amp', array(
+			'template_dir' => 'amp-templates',
+		) );
+		$this->assertFalse( amp_is_canonical() );
+		ob_start();
+		AMP_Theme_Support::amend_comment_form();
+		$output = ob_get_clean();
+		$this->assertContains( '<input type="hidden" name="redirect_to"', $output );
+		$this->assertContains( '<div submit-success>', $output );
+		$this->assertContains( '<div submit-error>', $output );
+	}
+
+	/**
+	 * Test filter_paired_template_hierarchy.
+	 *
+	 * @covers AMP_Theme_Support::filter_paired_template_hierarchy()
+	 */
+	public function test_filter_paired_template_hierarchy() {
+		$template_dir = 'amp-templates';
+		add_theme_support( 'amp', array(
+			'template_dir' => $template_dir,
+		) );
+		$templates          = array(
+			'single-post-example.php',
+			'single-post.php',
+			'single.php',
+		);
+		$filtered_templates = AMP_Theme_Support::filter_paired_template_hierarchy( $templates );
+		foreach ( $filtered_templates as $key => $filtered_template ) {
+			$this->assertEquals( $template_dir . '/' . $templates[ $key ], $filtered_template );
+		}
+	}
+
+	/**
+	 * Test filter_paired_template_include.
+	 *
+	 * @covers AMP_Theme_Support::filter_paired_template_include()
+	 */
+	public function test_filter_paired_template_include() {
+		$template_dir = 'amp-templates';
+		$template     = 'single.php';
+		add_theme_support( 'amp', array(
+			'template_dir' => $template_dir,
+		) );
+		$this->assertEquals( $template, AMP_Theme_Support::filter_paired_template_include( $template ) );
+		remove_theme_support( 'amp' );
+		try {
+			AMP_Theme_Support::filter_paired_template_include( $template );
+		} catch ( Exception $exception ) {
+			$e = $exception;
+		}
+		$this->assertTrue( isset( $e ) );
+	}
+
+	/**
+	 * Test get_current_canonical_url.
+	 *
+	 * @covers AMP_Theme_Support::get_current_canonical_url()
+	 */
+	public function test_get_current_canonical_url() {
+		global $post, $wp;
+		$home_url = home_url( '/' );
+		$this->assertEquals( $home_url, AMP_Theme_Support::get_current_canonical_url() );
+
+		$added_query_vars = array(
+			'foo' => 'bar',
+		);
+		$wp->query_vars   = $added_query_vars;
+		$this->assertEquals( add_query_arg( $added_query_vars, $home_url ), AMP_Theme_Support::get_current_canonical_url() );
+
+		$post = $this->factory()->post->create_and_get(); // WPCS: global override ok.
+		$this->go_to( get_permalink( $post ) );
+		$this->assertEquals( wp_get_canonical_url(), AMP_Theme_Support::get_current_canonical_url() );
+
+	}
+
+	/**
+	 * Test get_comment_form_state_id.
+	 *
+	 * @covers AMP_Theme_Support::get_comment_form_state_id()
+	 */
+	public function test_get_comment_form_state_id() {
+		$post_id = 54;
+		$this->assertEquals( 'commentform_post_' . $post_id, AMP_Theme_Support::get_comment_form_state_id( $post_id ) );
+		$post_id = 91542;
+		$this->assertEquals( 'commentform_post_' . $post_id, AMP_Theme_Support::get_comment_form_state_id( $post_id ) );
+	}
+
+	/**
+	 * Test filter_comment_form_defaults.
+	 *
+	 * @covers AMP_Theme_Support::filter_comment_form_defaults()
+	 */
+	public function test_filter_comment_form_defaults() {
+		global $post;
+		$post     = $this->factory()->post->create_and_get(); // WPCS: global override ok.
+		$defaults = AMP_Theme_Support::filter_comment_form_defaults( array(
+			'title_reply_to'      => 'Reply To',
+			'title_reply'         => 'Reply',
+			'cancel_reply_before' => '',
+			'title_reply_before'  => '',
+		) );
+		$this->assertContains( AMP_Theme_Support::get_comment_form_state_id( get_the_ID() ), $defaults['title_reply_before'] );
+		$this->assertContains( 'replyToName ?', $defaults['title_reply_before'] );
+		$this->assertContains( '</span>', $defaults['cancel_reply_before'] );
+	}
+
+	/**
+	 * Test filter_comment_reply_link.
+	 *
+	 * @covers AMP_Theme_Support::filter_comment_reply_link()
+	 */
+	public function test_filter_comment_reply_link() {
+		global $post;
+		$post          = $this->factory()->post->create_and_get(); // WPCS: global override ok.
+		$comment       = $this->factory()->comment->create_and_get();
+		$link          = get_comment_link( $comment );
+		$respond_id    = '5234';
+		$reply_text    = 'Reply';
+		$reply_to_text = 'Reply to';
+		$args          = compact( 'respond_id', 'reply_text', 'reply_to_text' );
+		$comment       = $this->factory()->comment->create_and_get();
+		update_option( 'comment_registration', true );
+		$filtered_link = AMP_Theme_Support::filter_comment_reply_link( $link, $args, $comment );
+		$this->assertEquals( $link, $filtered_link );
+		update_option( 'comment_registration', false );
+
+		$filtered_link = AMP_Theme_Support::filter_comment_reply_link( $link, $args, $comment );
+		$this->assertContains( AMP_Theme_Support::get_comment_form_state_id( get_the_ID() ), $filtered_link );
+		$this->assertContains( $comment->comment_author, $filtered_link );
+		$this->assertContains( $comment->comment_ID, $filtered_link );
+		$this->assertContains( 'tap:AMP.setState', $filtered_link );
+		$this->assertContains( $reply_text, $filtered_link );
+		$this->assertContains( $reply_to_text, $filtered_link );
+		$this->assertContains( $respond_id, $filtered_link );
+	}
+
+	/**
+	 * Test filter_cancel_comment_reply_link.
+	 *
+	 * @covers AMP_Theme_Support::filter_cancel_comment_reply_link()
+	 */
+	public function test_filter_cancel_comment_reply_link() {
+		global $post;
+		$post                   = $this->factory()->post->create_and_get(); // WPCS: global override ok.
+		$url                    = get_permalink( $post );
+		$_SERVER['REQUEST_URI'] = $url;
+		$this->factory()->comment->create_and_get();
+		$formatted_link = get_cancel_comment_reply_link();
+		$link           = remove_query_arg( 'replytocom' );
+		$text           = 'Cancel your reply';
+		$filtered_link  = AMP_Theme_Support::filter_cancel_comment_reply_link( $formatted_link, $link, $text );
+		$this->assertContains( $url, $filtered_link );
+		$this->assertContains( $text, $filtered_link );
+		$this->assertContains( '<a id="cancel-comment-reply-link"', $filtered_link );
+		$this->assertContains( '.values.comment_parent ==', $filtered_link );
+		$this->assertContains( 'tap:AMP.setState(', $filtered_link );
+
+		$filtered_link_no_text_passed = AMP_Theme_Support::filter_cancel_comment_reply_link( $formatted_link, $link, '' );
+		$this->assertContains( 'Click here to cancel reply.', $filtered_link_no_text_passed );
+	}
+
+	/**
+	 * Test print_amp_styles.
+	 *
+	 * @covers AMP_Theme_Support::print_amp_styles()
+	 */
+	public function test_print_amp_styles() {
+		ob_start();
+		AMP_Theme_Support::print_amp_styles();
+		$output = ob_get_clean();
+		$this->assertContains( amp_get_boilerplate_code(), $output );
+		$this->assertContains( '<style amp-custom></style>', $output );
+	}
+
+	/**
+	 * Test ensure_required_markup().
+	 *
+	 * @dataProvider get_script_data
+	 * @covers AMP_Theme_Support::ensure_required_markup()
+	 * @param string  $script The value of the script.
+	 * @param boolean $expected The expected result.
+	 */
+	public function test_ensure_required_markup( $script, $expected ) {
+		$page = '<html><head><script type="application/ld+json">%s</script></head><body>Test</body></html>';
+		$dom  = new DOMDocument();
+		$dom->loadHTML( sprintf( $page, $script ) );
+		AMP_Theme_Support::ensure_required_markup( $dom );
+		$this->assertEquals( $expected, substr_count( $dom->saveHTML(), 'schema.org' ) );
+	}
+
+	/**
+	 * Test dequeue_customize_preview_scripts.
+	 *
+	 * @covers AMP_Theme_Support::dequeue_customize_preview_scripts()
+	 */
+	public function test_dequeue_customize_preview_scripts() {
+		// Ensure AMP_Theme_Support::is_customize_preview_iframe() is true.
+		require_once ABSPATH . WPINC . '/class-wp-customize-manager.php';
+		$GLOBALS['wp_customize'] = new WP_Customize_Manager( array(
+			'messenger_channel' => 'baz',
+		) );
+		$GLOBALS['wp_customize']->start_previewing_theme();
+		$customize_preview = 'customize-preview';
+		$preview_style     = 'example-preview-style';
+		wp_enqueue_style( $preview_style, home_url( '/' ), array( $customize_preview ) );
+		AMP_Theme_Support::dequeue_customize_preview_scripts();
+		$this->assertTrue( wp_style_is( $preview_style ) );
+		$this->assertTrue( wp_style_is( $customize_preview ) );
+
+		wp_enqueue_style( $preview_style, home_url( '/' ), array( $customize_preview ) );
+		wp_enqueue_style( $customize_preview );
+		// Ensure AMP_Theme_Support::is_customize_preview_iframe() is false.
+		$GLOBALS['wp_customize'] = new WP_Customize_Manager();
+		AMP_Theme_Support::dequeue_customize_preview_scripts();
+		$this->assertFalse( wp_style_is( $preview_style ) );
+		$this->assertFalse( wp_style_is( $customize_preview ) );
+	}
+
+	/**
+	 * Test start_output_buffering.
+	 *
+	 * @covers AMP_Theme_Support::start_output_buffering()
+	 */
+	public function test_start_output_buffering() {
+		if ( ! function_exists( 'newrelic_disable_autorum ' ) ) {
+			/**
+			 * Define newrelic_disable_autorum to allow passing line.
+			 */
+			function newrelic_disable_autorum() {
+				return true;
+			}
+		}
+
+		add_theme_support( 'amp' );
+		AMP_Theme_Support::init();
+		AMP_Theme_Support::finish_init();
+
+		$ob_level = ob_get_level();
+		AMP_Theme_Support::start_output_buffering();
+
+		$this->assertEquals( 0, has_action( 'shutdown', array( self::TESTED_CLASS, 'finish_output_buffering' ) ) );
+		$this->assertTrue( ob_get_level() > $ob_level );
+
+		// End output buffer.
+		if ( ob_get_level() > $ob_level ) {
+			ob_get_clean();
+		}
+	}
+
+	/**
+	 * Test finish_output_buffering.
+	 *
+	 * @covers AMP_Theme_Support::finish_output_buffering()
+	 */
+	public function test_finish_output_buffering() {
+		add_theme_support( 'amp' );
+		AMP_Theme_Support::init();
+		AMP_Theme_Support::finish_init();
+
+		// start first layer buffer.
+		ob_start();
+		AMP_Theme_Support::start_output_buffering();
+
+		echo '<img src="test.png"><script data-test>document.write(\'Illegal\');</script>';
+
+		// Additional nested output bufferings which aren't getting closed.
+		ob_start();
+		echo 'foo';
+		ob_start( function( $response ) {
+			return strtoupper( $response );
+		} );
+		echo 'bar';
+
+		AMP_Theme_Support::finish_output_buffering();
+		// get first layer buffer.
+		$output = ob_get_clean();
+
+		$this->assertContains( '<html amp', $output );
+		$this->assertContains( 'foo', $output );
+		$this->assertContains( 'BAR', $output );
+		$this->assertContains( '<amp-img src="test.png"', $output );
+		$this->assertNotContains( '<script data-test', $output );
+
+	}
+
+	/**
+	 * Test filter_customize_partial_render.
+	 *
+	 * @covers AMP_Theme_Support::filter_customize_partial_render()
+	 */
+	public function test_filter_customize_partial_render() {
+		add_theme_support( 'amp' );
+		AMP_Theme_Support::init();
+		AMP_Theme_Support::finish_init();
+
+		$partial = '<img src="test.png"><script data-head>document.write(\'Illegal\');</script>';
+		$output  = AMP_Theme_Support::filter_customize_partial_render( $partial );
+		$this->assertContains( '<amp-img src="test.png"', $output );
+		$this->assertNotContains( '<script', $output );
+		$this->assertNotContains( '<html', $output );
+
+	}
+
 	/**
 	 * Test prepare_response.
 	 *
+	 * @global WP_Widget_Factory $wp_widget_factory
+	 * @global WP_Scripts $wp_scripts
 	 * @covers AMP_Theme_Support::prepare_response()
 	 */
 	public function test_prepare_response() {
+		global $wp_widget_factory, $wp_scripts, $wp_styles;
+		$wp_scripts = null;
+		$wp_styles  = null;
+
 		add_theme_support( 'amp' );
 		AMP_Theme_Support::init();
+		AMP_Theme_Support::finish_init();
+		$wp_widget_factory = new WP_Widget_Factory();
+		wp_widgets_init();
+
+		add_action( 'wp_enqueue_scripts', function() {
+			wp_enqueue_script( 'amp-list' );
+		} );
+		add_action( 'wp_print_scripts', function() {
+			echo '<!-- wp_print_scripts -->';
+		} );
+		add_filter( 'script_loader_tag', function( $tag, $handle ) {
+			return preg_replace( '/(?<=<script)/', " handle='$handle' ", $tag );
+		}, 10, 2 );
+		add_action( 'wp_footer', function() {
+			wp_print_scripts( 'amp-mathml' );
+			?>
+			<amp-mathml layout="container" data-formula="\[x = {-b \pm \sqrt{b^2-4ac} \over 2a}.\]"></amp-mathml>
+			<?php
+		}, 1 );
+
 		ob_start();
 		?>
 		<!DOCTYPE html>
 		<html amp <?php language_attributes(); ?>>
 			<head>
 				<?php wp_head(); ?>
-				<script data-head>document.write('TODO: This needs to be sanitized as well once.');</script>
+				<script data-head>document.write('Illegal');</script>
 			</head>
 			<body>
 				<img width="100" height="100" src="https://example.com/test.png">
@@ -114,18 +1008,29 @@ public function test_prepare_response() {
 					data-aax_src="302"></amp-ad>
 				<?php wp_footer(); ?>
 
+				<button onclick="alert('Illegal');">no-onclick</button>
+
 				<style>body { background: black; }</style>
 			</body>
 		</html>
 		<?php
 		$original_html  = trim( ob_get_clean() );
-		$sanitized_html = AMP_Theme_Support::prepare_response( $original_html );
+		$removed_nodes  = array();
+		$sanitized_html = AMP_Theme_Support::prepare_response( $original_html, array(
+			'validation_error_callback' => function( $removed ) use ( &$removed_nodes ) {
+				$removed_nodes[ $removed['node']->nodeName ] = $removed['node'];
+			},
+		) );
 
+		$this->assertNotContains( 'handle=', $sanitized_html );
+		$this->assertEquals( 2, substr_count( $sanitized_html, '<!-- wp_print_scripts -->' ) );
 		$this->assertContains( '<meta charset="' . get_bloginfo( 'charset' ) . '">', $sanitized_html );
 		$this->assertContains( '<meta name="viewport" content="width=device-width,minimum-scale=1">', $sanitized_html );
 		$this->assertContains( '<style amp-boilerplate>', $sanitized_html );
 		$this->assertContains( '<style amp-custom>body { background: black; }', $sanitized_html );
-		$this->assertContains( '<script async src="https://cdn.ampproject.org/v0.js"', $sanitized_html ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
+		$this->assertContains( '<script type="text/javascript" src="https://cdn.ampproject.org/v0.js" async></script>', $sanitized_html ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
+		$this->assertContains( '<script type="text/javascript" src="https://cdn.ampproject.org/v0/amp-list-latest.js" async custom-element="amp-list"></script>', $sanitized_html ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
+		$this->assertContains( '<script type="text/javascript" src="https://cdn.ampproject.org/v0/amp-mathml-latest.js" async custom-element="amp-mathml"></script>', $sanitized_html ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
 		$this->assertContains( '<meta name="generator" content="AMP Plugin', $sanitized_html );
 
 		$this->assertNotContains( '<img', $sanitized_html );
@@ -133,9 +1038,15 @@ public function test_prepare_response() {
 
 		$this->assertNotContains( '<audio', $sanitized_html );
 		$this->assertContains( '<amp-audio', $sanitized_html );
-		$this->assertContains( '<script async custom-element="amp-audio"', $sanitized_html );
 
-		$this->assertContains( '<script async custom-element="amp-ad"', $sanitized_html );
+		// Note these are single-quoted because they are injected after the DOM has been re-serialized, so the type and src attributes come from WP_Scripts::do_item().
+		$this->assertContains( '<script type=\'text/javascript\' src=\'https://cdn.ampproject.org/v0/amp-audio-latest.js\' async custom-element="amp-audio"></script>', $sanitized_html ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
+		$this->assertContains( '<script type=\'text/javascript\' src=\'https://cdn.ampproject.org/v0/amp-ad-latest.js\' async custom-element="amp-ad"></script>', $sanitized_html ); // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
+
+		$this->assertContains( '<button>no-onclick</button>', $sanitized_html );
+		$this->assertCount( 4, $removed_nodes );
+		$this->assertInstanceOf( 'DOMElement', $removed_nodes['script'] );
+		$this->assertInstanceOf( 'DOMAttr', $removed_nodes['onclick'] );
 	}
 
 	/**
@@ -182,71 +1093,77 @@ public function test_prepare_response_to_add_html5_doctype_and_amp_attribute() {
 	}
 
 	/**
-	 * Test purge_amp_query_vars.
+	 * Data provider for test_ensure_required_markup.
 	 *
-	 * @covers AMP_Theme_Support::purge_amp_query_vars()
+	 * @return array
 	 */
-	public function test_purge_amp_query_vars() {
-		// phpcs:disable WordPress.Security.NonceVerification.NoNonceVerification
-		$bad_query_vars = array(
-			'amp_latest_update_time' => '1517199956',
-			'__amp_source_origin'    => home_url(),
+	public function get_script_data() {
+		return array(
+			'schema_org_not_present'        => array(
+				'',
+				1,
+			),
+			'schema_org_present'            => array(
+				wp_json_encode( array( '@context' => 'http://schema.org' ) ),
+				1,
+			),
+			'schema_org_output_not_escaped' => array(
+				'{"@context":"http://schema.org"',
+				1,
+			),
+			'schema_org_another_key'        => array(
+				wp_json_encode( array( '@anothercontext' => 'https://schema.org' ) ),
+				1,
+			),
 		);
-		$ok_query_vars  = array(
-			'bar' => 'baz',
-		);
-		$all_query_vars = array_merge( $bad_query_vars, $ok_query_vars );
-
-		$_SERVER['QUERY_STRING'] = build_query( $all_query_vars );
-
-		remove_action( 'wp', 'amp_maybe_add_actions' );
-		$this->go_to( add_query_arg( $all_query_vars, home_url( '/foo/' ) ) );
-		$_REQUEST = $_GET; // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
-		foreach ( $all_query_vars as $key => $value ) {
-			$this->assertArrayHasKey( $key, $_GET ); // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
-			$this->assertArrayHasKey( $key, $_REQUEST ); // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
-			$this->assertContains( "$key=$value", $_SERVER['QUERY_STRING'] );
-			$this->assertContains( "$key=$value", $_SERVER['REQUEST_URI'] );
-		}
-
-		AMP_Theme_Support::$purged_amp_query_vars = array();
-		AMP_Theme_Support::purge_amp_query_vars();
-		$this->assertEqualSets( AMP_Theme_Support::$purged_amp_query_vars, $bad_query_vars );
+	}
 
-		foreach ( $bad_query_vars as $key => $value ) {
-			$this->assertArrayNotHasKey( $key, $_GET ); // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
-			$this->assertArrayNotHasKey( $key, $_REQUEST ); // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
-			$this->assertNotContains( "$key=$value", $_SERVER['QUERY_STRING'] );
-			$this->assertNotContains( "$key=$value", $_SERVER['REQUEST_URI'] );
-		}
-		foreach ( $ok_query_vars as $key => $value ) {
-			$this->assertArrayHasKey( $key, $_GET ); // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
-			$this->assertArrayHasKey( $key, $_REQUEST ); // phpcs:ignore WordPress.CSRF.NonceVerification.NoNonceVerification
-			$this->assertContains( "$key=$value", $_SERVER['QUERY_STRING'] );
-			$this->assertContains( "$key=$value", $_SERVER['REQUEST_URI'] );
-		}
-		// phpcs:enable WordPress.Security.NonceVerification.NoNonceVerification
+	/**
+	 * Test enqueue_assets().
+	 *
+	 * @covers AMP_Theme_Support::enqueue_assets()
+	 */
+	public function test_enqueue_assets() {
+		$script_slug = 'amp-runtime';
+		$style_slug  = 'amp-default';
+		wp_dequeue_script( $script_slug );
+		wp_dequeue_style( $style_slug );
+		AMP_Theme_Support::enqueue_assets();
+		$this->assertTrue( in_array( $script_slug, wp_scripts()->queue, true ) );
+		$this->assertTrue( in_array( $style_slug, wp_styles()->queue, true ) );
 	}
 
 	/**
-	 * Test get_amp_scripts().
+	 * Test AMP_Theme_Support::whitelist_layout_in_wp_kses_allowed_html().
 	 *
-	 * @covers AMP_Theme_Support::get_amp_scripts()
+	 * @see AMP_Theme_Support::whitelist_layout_in_wp_kses_allowed_html()
 	 */
-	public function test_get_amp_scripts() {
-		add_filter( 'amp_component_scripts', function( $scripts ) {
-			$scripts['amp-video'] = 'https://cdn.ampproject.org/v0/amp-video-0.1.js';
-			return $scripts;
-		} );
+	public function test_whitelist_layout_in_wp_kses_allowed_html() {
+		$attribute             = 'data-amp-layout';
+		$image_no_dimensions   = array(
+			'img' => array(
+				$attribute => true,
+			),
+		);
+		$image_with_dimensions = array_merge(
+			$image_no_dimensions,
+			array(
+				'height' => '100',
+				'width'  => '100',
+			)
+		);
 
-		$scripts = AMP_Theme_Support::get_amp_scripts( array(
-			'amp-mustache' => 'https://cdn.ampproject.org/v0/amp-mustache-0.1.js',
-			'amp-bind'     => 'https://cdn.ampproject.org/v0/amp-bind-0.1.js',
-		) );
+		$this->assertEquals( array(), AMP_Theme_Support::whitelist_layout_in_wp_kses_allowed_html( array() ) );
+		$this->assertEquals( $image_no_dimensions, AMP_Theme_Support::whitelist_layout_in_wp_kses_allowed_html( $image_no_dimensions ) );
 
-		$this->assertEquals(
-			'<script async src="https://cdn.ampproject.org/v0.js"></script><script async custom-template="amp-mustache" src="https://cdn.ampproject.org/v0/amp-mustache-0.1.js"></script><script async custom-element="amp-bind" src="https://cdn.ampproject.org/v0/amp-bind-0.1.js"></script><script async custom-element="amp-video" src="https://cdn.ampproject.org/v0/amp-video-0.1.js"></script>', // phpcs:ignore
-			$scripts
-		);
+		$context = AMP_Theme_Support::whitelist_layout_in_wp_kses_allowed_html( $image_with_dimensions );
+		$this->assertTrue( $context['img'][ $attribute ] );
+
+		$context = AMP_Theme_Support::whitelist_layout_in_wp_kses_allowed_html( $image_with_dimensions );
+		$this->assertTrue( $context['img'][ $attribute ] );
+
+		add_filter( 'wp_kses_allowed_html', 'AMP_Theme_Support::whitelist_layout_in_wp_kses_allowed_html', 10, 2 );
+		$image = '<img data-amp-layout="fill">';
+		$this->assertEquals( $image, wp_kses_post( $image ) );
 	}
 }
diff --git a/tests/test-class-amp-validation-utils.php b/tests/test-class-amp-validation-utils.php
index 16f90515019..6217f7c9323 100644
--- a/tests/test-class-amp-validation-utils.php
+++ b/tests/test-class-amp-validation-utils.php
@@ -12,6 +12,13 @@
  */
 class Test_AMP_Validation_Utils extends \WP_UnitTestCase {
 
+	/**
+	 * The name of the tested class.
+	 *
+	 * @var string
+	 */
+	const TESTED_CLASS = 'AMP_Validation_Utils';
+
 	/**
 	 * An instance of DOMElement to test.
 	 *
@@ -20,32 +27,39 @@ class Test_AMP_Validation_Utils extends \WP_UnitTestCase {
 	public $node;
 
 	/**
-	 * The expected REST API route.
+	 * A tag that the sanitizer should strip.
 	 *
 	 * @var string
 	 */
-	public $expected_route = '/amp-wp/v1/validate';
+	public $disallowed_tag = '<script async src="https://example.com/script"></script>'; // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
 
 	/**
-	 * A tag that the sanitizer should strip.
+	 * The name of a tag that the sanitizer should strip.
 	 *
 	 * @var string
 	 */
-	public $disallowed_tag = '<script async src="https://example.com/script"></script>'; // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
+	public $disallowed_tag_name = 'script';
 
 	/**
-	 * A valid image that sanitizers should not alter.
+	 * The name of an attribute that the sanitizer should strip.
+	 *
+	 * @var string
+	 */
+	public $disallowed_attribute_name = 'onload';
+
+	/**
+	 * A mock plugin name that outputs invalid markup.
 	 *
 	 * @var string
 	 */
-	public $valid_amp_img = '<amp-img id="img-123" media="(min-width: 600x)" src="/assets/example.jpg" width=200 height=500 layout="responsive"></amp-img>';
+	public $plugin_name = 'foo-bar';
 
 	/**
-	 * The key in the response for whether it has an AMP error.
+	 * A valid image that sanitizers should not alter.
 	 *
 	 * @var string
 	 */
-	public $error_key = 'has_error';
+	public $valid_amp_img = '<amp-img id="img-123" media="(min-width: 600x)" src="/assets/example.jpg" width="200" height="500" layout="responsive"></amp-img>';
 
 	/**
 	 * The name of the tag to test.
@@ -54,145 +68,153 @@ class Test_AMP_Validation_Utils extends \WP_UnitTestCase {
 	 */
 	const TAG_NAME = 'img';
 
+	/**
+	 * Backed up $wp_registered_widgets.
+	 *
+	 * @var array
+	 */
+	protected $original_wp_registered_widgets;
+
 	/**
 	 * Setup.
 	 *
 	 * @inheritdoc
+	 * @global $wp_registered_widgets
 	 */
 	public function setUp() {
 		parent::setUp();
 		$dom_document = new DOMDocument( '1.0', 'utf-8' );
 		$this->node   = $dom_document->createElement( self::TAG_NAME );
-		AMP_Validation_Utils::reset_removed();
+		AMP_Validation_Utils::reset_validation_results();
+		$this->original_wp_registered_widgets = $GLOBALS['wp_registered_widgets'];
+	}
+
+	/**
+	 * After a test method runs, reset any state in WordPress the test method might have changed.
+	 */
+	public function tearDown() {
+		$GLOBALS['wp_registered_widgets'] = $this->original_wp_registered_widgets; // WPCS: override ok.
+		parent::tearDown();
 	}
 
 	/**
 	 * Test init.
 	 *
-	 * @see AMP_Validation_Utils::init()
+	 * @covers AMP_Validation_Utils::init()
 	 */
 	public function test_init() {
-		$this->assertEquals( 10, has_action( 'rest_api_init', 'AMP_Validation_Utils::amp_rest_validation' ) );
-		$this->assertEquals( 10, has_action( 'save_post', 'AMP_Validation_Utils::validate_content' ) );
-		$this->assertEquals( 10, has_action( 'edit_form_top', 'AMP_Validation_Utils::display_error' ) );
+		add_theme_support( 'amp' );
+		AMP_Validation_Utils::init();
+		$this->assertEquals( 10, has_action( 'edit_form_top', self::TESTED_CLASS . '::print_edit_form_validation_status' ) );
+		$this->assertEquals( 10, has_action( 'init', self::TESTED_CLASS . '::register_post_type' ) );
+		$this->assertEquals( 10, has_action( 'all_admin_notices', self::TESTED_CLASS . '::plugin_notice' ) );
+		$this->assertEquals( 10, has_filter( 'manage_' . AMP_Validation_Utils::POST_TYPE_SLUG . '_posts_columns', self::TESTED_CLASS . '::add_post_columns' ) );
+		$this->assertEquals( 10, has_action( 'manage_posts_custom_column', self::TESTED_CLASS . '::output_custom_column' ) );
+		$this->assertEquals( 10, has_filter( 'post_row_actions', self::TESTED_CLASS . '::filter_row_actions' ) );
+		$this->assertEquals( 10, has_filter( 'bulk_actions-edit-' . AMP_Validation_Utils::POST_TYPE_SLUG, self::TESTED_CLASS . '::add_bulk_action' ) );
+		$this->assertEquals( 10, has_filter( 'handle_bulk_actions-edit-' . AMP_Validation_Utils::POST_TYPE_SLUG, self::TESTED_CLASS . '::handle_bulk_action' ) );
+		$this->assertEquals( 10, has_action( 'admin_notices', self::TESTED_CLASS . '::remaining_error_notice' ) );
+		$this->assertEquals( 10, has_action( 'admin_menu', self::TESTED_CLASS . '::remove_publish_meta_box' ) );
+		$this->assertEquals( 10, has_action( 'add_meta_boxes', self::TESTED_CLASS . '::add_meta_boxes' ) );
 	}
 
 	/**
-	 * Test track_removed.
+	 * Test init.
 	 *
-	 * @see AMP_Validation_Utils::track_removed()
+	 * @covers AMP_Validation_Utils::add_validation_hooks()
 	 */
-	public function test_track_removed() {
-		$attr_name              = 'invalid-attr';
-		$expected_removed_attrs = array(
-			$attr_name => 1,
-		);
-		$expected_removed_nodes = array(
-			'img' => 1,
-		);
-		$this->assertEmpty( AMP_Validation_Utils::$removed_attributes );
-		$this->assertEmpty( AMP_Validation_Utils::$removed_nodes );
-		AMP_Validation_Utils::track_removed( $this->node, AMP_Validation_Utils::ATTRIBUTE_REMOVED, $attr_name );
-		$this->assertEquals( $expected_removed_attrs, AMP_Validation_Utils::$removed_attributes );
-		AMP_Validation_Utils::track_removed( $this->node, AMP_Validation_Utils::NODE_REMOVED );
-		$this->assertEquals( $expected_removed_nodes, AMP_Validation_Utils::$removed_nodes );
+	public function test_add_validation_hooks() {
+		AMP_Validation_Utils::add_validation_hooks();
+		$this->assertEquals( PHP_INT_MAX, has_filter( 'the_content', array( self::TESTED_CLASS, 'decorate_filter_source' ) ) );
+		$this->assertEquals( PHP_INT_MAX, has_filter( 'the_excerpt', array( self::TESTED_CLASS, 'decorate_filter_source' ) ) );
+		$this->assertEquals( 10, has_action( 'amp_content_sanitizers', array( self::TESTED_CLASS, 'add_validation_callback' ) ) );
+		$this->assertEquals( -1, has_action( 'do_shortcode_tag', array( self::TESTED_CLASS, 'decorate_shortcode_source' ) ) );
 	}
 
 	/**
-	 * Test increment_count.
+	 * Test add_validation_error.
 	 *
-	 * @see AMP_Validation_Utils::increment_count()
+	 * @covers AMP_Validation_Utils::add_validation_error()
 	 */
-	public function test_increment_count() {
-		$attribute     = 'script';
-		$one_attribute = array(
-			$attribute => 1,
-		);
-		$expected      = array(
-			$attribute => 2,
+	public function test_track_removed() {
+		$this->assertEmpty( AMP_Validation_Utils::$validation_errors );
+		AMP_Validation_Utils::add_validation_error( array(
+			'node' => $this->node,
+		) );
+
+		$this->assertEquals(
+			array(
+				array(
+					'node_name'       => 'img',
+					'sources'         => array(),
+					'code'            => AMP_Validation_Utils::INVALID_ELEMENT_CODE,
+					'node_attributes' => array(),
+				),
+			),
+			AMP_Validation_Utils::$validation_errors
 		);
-		$this->assertEquals( $one_attribute, AMP_Validation_Utils::increment_count( array(), $attribute ) );
-		$this->assertEquals( $expected, AMP_Validation_Utils::increment_count( $one_attribute, $attribute ) );
+		AMP_Validation_Utils::reset_validation_results();
 	}
 
 	/**
 	 * Test was_node_removed.
 	 *
-	 * @see AMP_Validation_Utils::was_node_removed()
+	 * @covers AMP_Validation_Utils::add_validation_error()
 	 */
 	public function test_was_node_removed() {
-		$attr_name = 'invalid-attr';
-		$this->assertFalse( AMP_Validation_Utils::was_node_removed() );
-		AMP_Validation_Utils::track_removed( $this->node, AMP_Validation_Utils::NODE_REMOVED );
-		$this->assertTrue( AMP_Validation_Utils::was_node_removed() );
+		$this->assertEmpty( AMP_Validation_Utils::$validation_errors );
+		AMP_Validation_Utils::add_validation_error(
+			array(
+				'node' => $this->node,
+			)
+		);
+		$this->assertNotEmpty( AMP_Validation_Utils::$validation_errors );
 	}
 
 	/**
 	 * Test process_markup.
 	 *
-	 * @see AMP_Validation_Utils::process_markup()
+	 * @covers AMP_Validation_Utils::process_markup()
 	 */
 	public function test_process_markup() {
-		$this->set_authorized();
+		$this->set_capability();
 		AMP_Validation_Utils::process_markup( $this->valid_amp_img );
-		$this->assertEquals( null, AMP_Validation_Utils::$removed_nodes );
-		$this->assertEquals( null, AMP_Validation_Utils::$removed_attributes );
+		$this->assertEquals( array(), AMP_Validation_Utils::$validation_errors );
 
-		AMP_Validation_Utils::reset_removed();
+		AMP_Validation_Utils::reset_validation_results();
 		$video = '<video src="https://example.com/video">';
-		AMP_Validation_Utils::process_markup( $this->valid_amp_img );
+		AMP_Validation_Utils::process_markup( $video );
 		// This isn't valid AMP, but the sanitizer should convert it to an <amp-video>, without stripping anything.
-		$this->assertEquals( null, AMP_Validation_Utils::$removed_nodes );
-		$this->assertEquals( null, AMP_Validation_Utils::$removed_attributes );
+		$this->assertEquals( array(), AMP_Validation_Utils::$validation_errors );
 
-		AMP_Validation_Utils::reset_removed();
+		AMP_Validation_Utils::reset_validation_results();
 
 		AMP_Validation_Utils::process_markup( $this->disallowed_tag );
-		$this->assertEquals( 1, AMP_Validation_Utils::$removed_nodes['script'] );
-		$this->assertEquals( null, AMP_Validation_Utils::$removed_attributes );
+		$this->assertCount( 1, AMP_Validation_Utils::$validation_errors );
+		$this->assertEquals( 'script', AMP_Validation_Utils::$validation_errors[0]['node_name'] );
 
-		AMP_Validation_Utils::reset_removed();
+		AMP_Validation_Utils::reset_validation_results();
 		$disallowed_style = '<div style="display:none"></div>';
 		AMP_Validation_Utils::process_markup( $disallowed_style );
-		$removed_attribute = AMP_Validation_Utils::$removed_attributes;
-		$this->assertEquals( null, AMP_Validation_Utils::$removed_nodes );
-		$this->assertEquals( null, $removed_attribute );
+		$this->assertEquals( array(), AMP_Validation_Utils::$validation_errors );
 
-		AMP_Validation_Utils::reset_removed();
+		AMP_Validation_Utils::reset_validation_results();
 		$invalid_video = '<video width="200" height="100"></video>';
 		AMP_Validation_Utils::process_markup( $invalid_video );
-		$removed_node = AMP_Validation_Utils::$removed_nodes;
-		$this->assertEquals( 1, AMP_Validation_Utils::$removed_nodes['video'] ); // phpcs:ignore WordPress.NamingConventions.ValidVariableName.NotSnakeCaseMemberVar.
-		$this->assertEquals( null, AMP_Validation_Utils::$removed_attributes );
-	}
+		$this->assertCount( 1, AMP_Validation_Utils::$validation_errors );
+		$this->assertEquals( 'video', AMP_Validation_Utils::$validation_errors[0]['node_name'] );
+		AMP_Validation_Utils::reset_validation_results();
 
-	/**
-	 * Test amp_rest_validation.
-	 *
-	 * @see AMP_Validation_Utils::amp_rest_validation()
-	 */
-	public function test_amp_rest_validation() {
-		$routes  = rest_get_server()->get_routes();
-		$route   = $routes[ $this->expected_route ][0];
-		$methods = array(
-			'POST' => true,
-		);
-		$args    = array(
-			'markup' => array(
-				'validate_callback' => array( 'AMP_Validation_Utils', 'validate_arg' ),
-			),
-		);
-
-		$this->assertEquals( $args, $route['args'] );
-		$this->assertEquals( array( 'AMP_Validation_Utils', 'validate_markup' ), $route['callback'] );
-		$this->assertEquals( $methods, $route['methods'] );
-		$this->assertEquals( array( 'AMP_Validation_Utils', 'has_cap' ), $route['permission_callback'] );
+		AMP_Validation_Utils::process_markup( '<button onclick="evil()">Do it</button>' );
+		$this->assertCount( 1, AMP_Validation_Utils::$validation_errors );
+		$this->assertEquals( 'onclick', AMP_Validation_Utils::$validation_errors[0]['node_name'] );
+		AMP_Validation_Utils::reset_validation_results();
 	}
 
 	/**
 	 * Test has_cap.
 	 *
-	 * @see AMP_Validation_Utils::has_cap()
+	 * @covers AMP_Validation_Utils::has_cap()
 	 */
 	public function test_has_cap() {
 		wp_set_current_user( $this->factory()->user->create( array(
@@ -200,159 +222,1141 @@ public function test_has_cap() {
 		) ) );
 		$this->assertFalse( AMP_Validation_Utils::has_cap() );
 
-		wp_set_current_user( $this->factory()->user->create( array(
-			'role' => 'administrator',
-		) ) );
+		$this->set_capability();
 		$this->assertTrue( AMP_Validation_Utils::has_cap() );
 	}
 
 	/**
-	 * Test validate_markup.
+	 * Test get_response.
 	 *
-	 * @see AMP_Validation_Utils::validate_markup()
+	 * @covers AMP_Validation_Utils::summarize_validation_errors()
 	 */
-	public function test_validate_markup() {
-		$this->set_authorized();
-		$request = new WP_REST_Request( 'POST', $this->expected_route );
-		$request->set_header( 'content-type', 'application/json' );
-		$request->set_body( wp_json_encode( array(
-			AMP_Validation_Utils::MARKUP_KEY => $this->disallowed_tag,
-		) ) );
-		$response          = AMP_Validation_Utils::validate_markup( $request );
+	public function test_summarize_validation_errors() {
+		global $post;
+		$post = $this->factory()->post->create_and_get(); // WPCS: global override ok.
+		AMP_Validation_Utils::process_markup( $this->disallowed_tag );
+		$response = AMP_Validation_Utils::summarize_validation_errors( AMP_Validation_Utils::$validation_errors );
+		AMP_Validation_Utils::reset_validation_results();
 		$expected_response = array(
-			$this->error_key     => true,
-			'removed_nodes'      => array(
+			AMP_Validation_Utils::REMOVED_ELEMENTS   => array(
 				'script' => 1,
 			),
-			'removed_attributes' => null,
-			'processed_markup'   => $this->disallowed_tag,
+			AMP_Validation_Utils::REMOVED_ATTRIBUTES => array(),
+			'sources_with_invalid_output'            => array(),
 		);
 		$this->assertEquals( $expected_response, $response );
+	}
+
+	/**
+	 * Test reset_validation_results.
+	 *
+	 * @covers AMP_Validation_Utils::reset_validation_results()
+	 */
+	public function test_reset_validation_results() {
+		AMP_Validation_Utils::add_validation_error( array(
+			'code' => 'test',
+		) );
+		AMP_Validation_Utils::reset_validation_results();
+		$this->assertEquals( array(), AMP_Validation_Utils::$validation_errors );
+	}
+
+	/**
+	 * Test print_edit_form_validation_status
+	 *
+	 * @covers AMP_Validation_Utils::print_edit_form_validation_status()
+	 */
+	public function test_print_edit_form_validation_status() {
+		$this->set_capability();
+		$post = $this->factory()->post->create_and_get();
+		ob_start();
+		AMP_Validation_Utils::print_edit_form_validation_status( $post );
+		$output = ob_get_clean();
+
+		$this->assertNotContains( 'notice notice-warning', $output );
+		$this->assertNotContains( 'Warning:', $output );
+
+		$post->post_content = $this->disallowed_tag;
+		ob_start();
+		AMP_Validation_Utils::print_edit_form_validation_status( $post );
+		$output = ob_get_clean();
+
+		$this->assertContains( 'notice notice-warning', $output );
+		$this->assertContains( 'Warning:', $output );
+		$this->assertContains( '<code>script</code>', $output );
+		AMP_Validation_Utils::reset_validation_results();
+
+		$youtube            = 'https://www.youtube.com/watch?v=GGS-tKTXw4Y';
+		$post->post_content = $youtube;
+		ob_start();
+		AMP_Validation_Utils::print_edit_form_validation_status( $post );
+		$output = ob_get_clean();
+
+		// The YouTube embed handler should convert the URL into a valid AMP element.
+		$this->assertNotContains( 'notice notice-warning', $output );
+		$this->assertNotContains( 'Warning:', $output );
+		AMP_Validation_Utils::reset_validation_results();
+	}
+
+	/**
+	 * Test source comments.
+	 *
+	 * @covers AMP_Validation_Utils::locate_sources()
+	 * @covers AMP_Validation_Utils::parse_source_comment()
+	 * @covers AMP_Validation_Utils::get_source_comment()
+	 * @covers AMP_Validation_Utils::remove_source_comments()
+	 */
+	public function test_source_comments() {
+		$source1 = array(
+			'type'      => 'plugin',
+			'name'      => 'foo',
+			'shortcode' => 'test',
+			'function'  => __FUNCTION__,
+		);
+		$source2 = array(
+			'type'     => 'theme',
+			'name'     => 'bar',
+			'function' => __FUNCTION__,
+			'hook'     => 'something',
+		);
+
+		$dom = AMP_DOM_Utils::get_dom_from_content( implode(
+			'',
+			array(
+				AMP_Validation_Utils::get_source_comment( $source1, true ),
+				AMP_Validation_Utils::get_source_comment( $source2, true ),
+				'<b id="test">Test</b>',
+				AMP_Validation_Utils::get_source_comment( $source2, false ),
+				AMP_Validation_Utils::get_source_comment( $source1, false ),
+			)
+		) );
+
+		/**
+		 * Comments.
+		 *
+		 * @var DOMComment[] $comments
+		 */
+		$comments = array();
+		$xpath    = new DOMXPath( $dom );
+		foreach ( $xpath->query( '//comment()' ) as $comment ) {
+			$comments[] = $comment;
+		}
+		$this->assertCount( 4, $comments );
+
+		$sources = AMP_Validation_Utils::locate_sources( $dom->getElementById( 'test' ) );
+		$this->assertInternalType( 'array', $sources );
+		$this->assertCount( 2, $sources );
+
+		$this->assertEquals( $source1, $sources[0] );
+		$parsed_comment = AMP_Validation_Utils::parse_source_comment( $comments[0] );
+		$this->assertEquals( $source1, $parsed_comment['source'] );
+		$this->assertFalse( $parsed_comment['closing'] );
+		$parsed_comment = AMP_Validation_Utils::parse_source_comment( $comments[3] );
+		$this->assertEquals( $source1, $parsed_comment['source'] );
+		$this->assertTrue( $parsed_comment['closing'] );
+
+		$this->assertEquals( $source2, $sources[1] );
+		$parsed_comment = AMP_Validation_Utils::parse_source_comment( $comments[1] );
+		$this->assertEquals( $source2, $parsed_comment['source'] );
+		$this->assertFalse( $parsed_comment['closing'] );
+		$parsed_comment = AMP_Validation_Utils::parse_source_comment( $comments[2] );
+		$this->assertEquals( $source2, $parsed_comment['source'] );
+		$this->assertTrue( $parsed_comment['closing'] );
+
+		AMP_Validation_Utils::remove_source_comments( $dom );
+		$this->assertEquals( 0, $xpath->query( '//comment()' )->length );
+	}
+
+	/**
+	 * Test wrap_widget_callbacks.
+	 *
+	 * @covers AMP_Validation_Utils::wrap_widget_callbacks()
+	 */
+	public function test_wrap_widget_callbacks() {
+		global $wp_registered_widgets, $_wp_sidebars_widgets;
+
+		$widget_id = 'search-2';
+		$this->assertArrayHasKey( $widget_id, $wp_registered_widgets );
+		$this->assertInternalType( 'array', $wp_registered_widgets[ $widget_id ]['callback'] );
+		$this->assertInstanceOf( 'WP_Widget_Search', $wp_registered_widgets[ $widget_id ]['callback'][0] );
+
+		AMP_Validation_Utils::wrap_widget_callbacks();
+		$this->assertInstanceOf( 'Closure', $wp_registered_widgets[ $widget_id ]['callback'] );
+
+		$sidebar_id = 'amp-sidebar';
+		register_sidebar( array(
+			'id'           => $sidebar_id,
+			'after_widget' => '</li>',
+		) );
+		$_wp_sidebars_widgets[ $sidebar_id ] = array( $widget_id ); // WPCS: global override ok.
+
+		ob_start();
+		dynamic_sidebar( $sidebar_id );
+		$output = ob_get_clean();
+
+		$this->assertStringStartsWith(
+			'<!--amp-source-stack {"type":"core","name":"wp-includes","function":"WP_Widget_Search::display_callback","widget_id":"search-2"}--><li id="search-2"',
+			$output
+		);
+		$this->assertStringEndsWith(
+			'</li><!--/amp-source-stack {"type":"core","name":"wp-includes","function":"WP_Widget_Search::display_callback","widget_id":"search-2"}-->',
+			$output
+		);
+	}
+
+	/**
+	 * Test wrap_hook_callbacks.
+	 *
+	 * @covers AMP_Validation_Utils::wrap_hook_callbacks()
+	 */
+	public function test_callback_wrappers() {
+		global $post;
+		$that = $this;
+		$post = $this->factory()->post->create_and_get(); // WPCS: global override ok.
+		$this->set_capability();
+		$action_no_tag_output     = 'foo_action';
+		$action_core_output       = 'core_action';
+		$action_no_output         = 'bar_action_no_output';
+		$action_function_callback = 'baz_action_function';
+		$action_no_argument       = 'test_action_no_argument';
+		$action_one_argument      = 'baz_action_one_argument';
+		$action_two_arguments     = 'example_action_two_arguments';
+		$notice                   = 'Example notice';
+
+		AMP_Validation_Utils::add_validation_hooks();
+
+		add_action( $action_function_callback, '_amp_print_php_version_admin_notice' );
+		add_action( $action_no_argument, array( $this, 'output_div' ) );
+		add_action( $action_one_argument, array( $this, 'output_notice' ) );
+		add_action( $action_two_arguments, array( $this, 'output_message' ), 10, 2 );
+		add_action( $action_no_output, array( $this, 'get_string' ), 10, 2 );
+		add_action( $action_no_tag_output, 'the_ID' );
+		add_action( $action_core_output, 'edit_post_link' );
+		add_action( $action_no_output, '__return_false' );
+
+		// All of the callback functions remain as-is. They will only change for a given hook at the 'all' action.
+		$this->assertEquals( 10, has_action( $action_no_tag_output, 'the_ID' ) );
+		$this->assertEquals( 10, has_action( $action_no_output, array( $this, 'get_string' ) ) );
+		$this->assertEquals( 10, has_action( $action_no_argument, array( $this, 'output_div' ) ) );
+		$this->assertEquals( 10, has_action( $action_one_argument, array( $this, 'output_notice' ) ) );
+		$this->assertEquals( 10, has_action( $action_two_arguments, array( $this, 'output_message' ) ) );
+
+		ob_start();
+		do_action( $action_function_callback );
+		$output = ob_get_clean();
+		$this->assertContains( '<div class="notice notice-error">', $output );
+		$this->assertContains( '<!--amp-source-stack {"type":"plugin","name":"amp"', $output );
+		$this->assertContains( '<!--/amp-source-stack {"type":"plugin","name":"amp"', $output );
+
+		ob_start();
+		do_action( $action_no_argument );
+		$output = ob_get_clean();
+		$this->assertContains( '<div></div>', $output );
+		$this->assertContains( '<!--amp-source-stack {"type":"plugin","name":"amp"', $output );
+		$this->assertContains( '<!--/amp-source-stack {"type":"plugin","name":"amp"', $output );
+
+		ob_start();
+		do_action( $action_one_argument, $notice );
+		$output = ob_get_clean();
+		$this->assertContains( $notice, $output );
+		$this->assertContains( sprintf( '<div class="notice notice-warning"><p>%s</p></div>', $notice ), $output );
+		$this->assertContains( '<!--amp-source-stack {"type":"plugin","name":"amp"', $output );
+		$this->assertContains( '<!--/amp-source-stack {"type":"plugin","name":"amp"', $output );
+
+		ob_start();
+		do_action( $action_two_arguments, $notice, get_the_ID() );
+		$output = ob_get_clean();
+		ob_start();
+		self::output_message( $notice, get_the_ID() );
+		$expected_output = ob_get_clean();
+		$this->assertContains( $expected_output, $output );
+		$this->assertContains( '<!--amp-source-stack {"type":"plugin","name":"amp"', $output );
+		$this->assertContains( '<!--/amp-source-stack {"type":"plugin","name":"amp"', $output );
+
+		// This action's callback doesn't output any HTML tags, so no HTML should be present.
+		ob_start();
+		do_action( $action_no_tag_output );
+		$output = ob_get_clean();
+		$this->assertNotContains( '<!--amp-source-stack ', $output );
+		$this->assertNotContains( '<!--/amp-source-stack ', $output );
+
+		// This action's callback comes from core.
+		ob_start();
+		do_action( $action_core_output );
+		$output = ob_get_clean();
+		$this->assertContains( '<!--amp-source-stack {"type":"core","name":"wp-includes"', $output );
+		$this->assertContains( '<!--/amp-source-stack {"type":"core","name":"wp-includes"', $output );
+
+		// This action's callback doesn't echo any markup, so it shouldn't be wrapped in comments.
+		ob_start();
+		do_action( $action_no_output );
+		$output = ob_get_clean();
+		$this->assertNotContains( '<!--amp-source-stack ', $output );
+		$this->assertNotContains( '<!--/amp-source-stack ', $output );
+
+		// Ensure that nested actions output the expected stack, and that has_action() works as expected in spite of the function wrapping.
+		$handle_outer_action = function() use ( $that, &$handle_outer_action, &$handle_inner_action ) {
+			$that->assertEquals( 10, has_action( 'outer_action', $handle_outer_action ) );
+			$that->assertEquals( 10, has_action( 'inner_action', $handle_inner_action ) );
+			do_action( 'inner_action' );
+			$that->assertEquals( 10, has_action( 'inner_action', $handle_inner_action ) );
+		};
+		$handle_inner_action = function() use ( $that, &$handle_outer_action, &$handle_inner_action ) {
+			$that->assertEquals( 10, has_action( 'outer_action', $handle_outer_action ) );
+			$that->assertEquals( 10, has_action( 'inner_action', $handle_inner_action ) );
+			echo '<b>Hello</b>';
+		};
+		add_action( 'outer_action', $handle_outer_action );
+		add_action( 'inner_action', $handle_inner_action );
+		ob_start();
+		do_action( 'outer_action' );
+		$output = ob_get_clean();
+		$this->assertEquals(
+			implode( '', array(
+				'<!--amp-source-stack {"type":"plugin","name":"amp","function":"{closure}","hook":"outer_action"}-->',
+				'<!--amp-source-stack {"type":"plugin","name":"amp","function":"{closure}","hook":"inner_action"}-->',
+				'<b>Hello</b>',
+				'<!--/amp-source-stack {"type":"plugin","name":"amp","function":"{closure}","hook":"inner_action"}-->',
+				'<!--/amp-source-stack {"type":"plugin","name":"amp","function":"{closure}","hook":"outer_action"}-->',
+			) ),
+			$output
+		);
+	}
+
+	/**
+	 * Test decorate_shortcode_source.
+	 *
+	 * @covers AMP_Validation_Utils::decorate_shortcode_source()
+	 * @covers AMP_Validation_Utils::decorate_filter_source()
+	 */
+	public function test_decorate_shortcode_and_filter_source() {
+		AMP_Validation_Utils::add_validation_hooks();
+		add_shortcode( 'test', function() {
+			return '<b>test</b>';
+		} );
+
+		$filtered_content = apply_filters( 'the_content', 'before[test]after' );
+		$source_json      = '{"hook":"the_content","filter":true,"sources":[{"type":"core","name":"wp-includes","function":"WP_Embed::run_shortcode"},{"type":"core","name":"wp-includes","function":"WP_Embed::autoembed"},{"type":"core","name":"wp-includes","function":"wptexturize"},{"type":"core","name":"wp-includes","function":"wpautop"},{"type":"core","name":"wp-includes","function":"shortcode_unautop"},{"type":"core","name":"wp-includes","function":"prepend_attachment"},{"type":"core","name":"wp-includes","function":"wp_make_content_images_responsive"},{"type":"core","name":"wp-includes","function":"capital_P_dangit"},{"type":"core","name":"wp-includes","function":"do_shortcode"},{"type":"core","name":"wp-includes","function":"convert_smilies"}]}';
+		$expected_content = implode( '', array(
+			"<!--amp-source-stack $source_json>",
+			'<p>before<!--amp-source-stack {"type":"plugin","name":"amp","function":"{closure}","shortcode":"test"}--><b>test</b><!--/amp-source-stack {"type":"plugin","name":"amp","function":"{closure}","shortcode":"test"}-->after</p>' . "\n",
+			"<!--/amp-source-stack $source_json>",
+		) );
+	}
+
+	/**
+	 * Test get_source
+	 *
+	 * @covers AMP_Validation_Utils::get_source()
+	 */
+	public function test_get_source() {
+		$source = AMP_Validation_Utils::get_source( 'amp_after_setup_theme' );
+		$this->assertEquals( 'amp', $source['name'] );
+		$this->assertEquals( 'plugin', $source['type'] );
+
+		$source = AMP_Validation_Utils::get_source( 'the_content' );
+		$this->assertEquals( 'wp-includes', $source['name'] );
+		$this->assertEquals( 'core', $source['type'] );
+	}
+
+	/**
+	 * Test wrapped_callback
+	 *
+	 * @covers AMP_Validation_Utils::wrapped_callback()
+	 */
+	public function test_wrapped_callback() {
+		$test_string = "<b class='\nfoo\nbar\n'>Cool!</b>";
+		$callback    = array(
+			'function'      => function() use ( $test_string ) {
+				echo $test_string; // WPCS: XSS OK.
+			},
+			'accepted_args' => 0,
+			'source'        => array(
+				'type' => 'plugin',
+				'name' => 'amp',
+				'hook' => 'bar',
+			),
+		);
+
+		$wrapped_callback = AMP_Validation_Utils::wrapped_callback( $callback );
+		$this->assertTrue( $wrapped_callback instanceof Closure );
+		ob_start();
+		call_user_func( $wrapped_callback );
+		$output = ob_get_clean();
+
+		$this->assertEquals( 'Closure', get_class( $wrapped_callback ) );
+		$this->assertContains( $test_string, $output );
+		$this->assertContains( '<!--amp-source-stack {"type":"plugin","name":"amp","hook":"bar"}', $output );
+		$this->assertContains( '<!--/amp-source-stack {"type":"plugin","name":"amp","hook":"bar"}', $output );
+
+		$callback = array(
+			'function'      => array( $this, 'get_string' ),
+			'accepted_args' => 0,
+			'source'        => array(
+				'type' => 'plugin',
+				'name' => 'amp',
+				'hook' => 'bar',
+			),
+		);
 
-		$request->set_body( wp_json_encode( array(
-			AMP_Validation_Utils::MARKUP_KEY => $this->valid_amp_img,
+		$wrapped_callback = AMP_Validation_Utils::wrapped_callback( $callback );
+		$this->assertTrue( $wrapped_callback instanceof Closure );
+		ob_start();
+		$result = call_user_func( $wrapped_callback );
+		$output = ob_get_clean();
+		$this->assertEquals( 'Closure', get_class( $wrapped_callback ) );
+		$this->assertEquals( '', $output );
+		$this->assertEquals( call_user_func( array( $this, 'get_string' ) ), $result );
+		unset( $post );
+	}
+
+	/**
+	 * Add a nonce to the $_REQUEST, so that is_authorized() returns true.
+	 *
+	 * @return void
+	 */
+	public function set_capability() {
+		wp_set_current_user( $this->factory()->user->create( array(
+			'role' => 'administrator',
 		) ) );
-		$response          = AMP_Validation_Utils::validate_markup( $request );
-		$expected_response = array(
-			$this->error_key     => false,
-			'removed_nodes'      => null,
-			'removed_attributes' => null,
-			'processed_markup'   => $this->valid_amp_img,
+	}
+
+	/**
+	 * Outputs a div.
+	 *
+	 * @return void
+	 */
+	public function output_div() {
+		echo '<div></div>';
+	}
+
+	/**
+	 * Outputs a notice.
+	 *
+	 * @param string $message The message to output.
+	 *
+	 * @return void
+	 */
+	public function output_notice( $message ) {
+		printf( '<div class="notice notice-warning"><p>%s</p></div>', esc_attr( $message ) );
+	}
+
+	/**
+	 * Outputs a message with an excerpt.
+	 *
+	 * @param string $message The message to output.
+	 * @param string $id The ID of the post.
+	 *
+	 * @return void
+	 */
+	public function output_message( $message, $id ) {
+		printf( '<<p>%s</p><p>%s</p>', esc_attr( $message ), esc_html( $id ) );
+	}
+
+	/**
+	 * Gets a string.
+	 *
+	 * @return string
+	 */
+	public function get_string() {
+		return 'Example string';
+	}
+
+	/**
+	 * Test should_validate_response.
+	 *
+	 * @covers AMP_Validation_Utils::should_validate_response()
+	 */
+	public function test_should_validate_response() {
+		global $post;
+		$post = $this->factory()->post->create(); // WPCS: global override ok.
+		$this->assertFalse( AMP_Validation_Utils::should_validate_response() );
+		$_GET[ AMP_Validation_Utils::VALIDATE_QUERY_VAR ] = 1;
+		$this->assertFalse( AMP_Validation_Utils::should_validate_response() );
+		$this->set_capability();
+		$this->assertTrue( AMP_Validation_Utils::should_validate_response() );
+	}
+
+	/**
+	 * Test add_validation_callback
+	 *
+	 * @covers AMP_Validation_Utils::add_validation_callback()
+	 */
+	public function test_add_validation_callback() {
+		global $post;
+		$post       = $this->factory()->post->create_and_get(); // WPCS: global override ok.
+		$sanitizers = array(
+			'AMP_Img_Sanitizer'      => array(),
+			'AMP_Form_Sanitizer'     => array(),
+			'AMP_Comments_Sanitizer' => array(),
 		);
-		$this->assertEquals( $expected_response, $response );
+
+		$expected_callback   = self::TESTED_CLASS . '::add_validation_error';
+		$filtered_sanitizers = AMP_Validation_Utils::add_validation_callback( $sanitizers );
+		foreach ( $filtered_sanitizers as $sanitizer => $args ) {
+			$this->assertEquals( $expected_callback, $args['validation_error_callback'] );
+		}
+		remove_theme_support( 'amp' );
 	}
 
 	/**
-	 * Test get_response.
+	 * Test for register_post_type()
 	 *
-	 * @see AMP_Validation_Utils::get_response()
+	 * @covers AMP_Validation_Utils::register_post_type()
 	 */
-	public function test_get_response() {
-		$this->set_authorized();
-		$response          = AMP_Validation_Utils::get_response( $this->disallowed_tag );
-		$expected_response = array(
-			$this->error_key     => true,
-			'removed_nodes'      => array(
-				'script' => 1,
+	public function test_register_post_type() {
+		AMP_Validation_Utils::register_post_type();
+		$amp_post_type = get_post_type_object( AMP_Validation_Utils::POST_TYPE_SLUG );
+
+		$this->assertTrue( in_array( AMP_Validation_Utils::POST_TYPE_SLUG, get_post_types(), true ) );
+		$this->assertEquals( array(), get_all_post_type_supports( AMP_Validation_Utils::POST_TYPE_SLUG ) );
+		$this->assertEquals( AMP_Validation_Utils::POST_TYPE_SLUG, $amp_post_type->name );
+		$this->assertEquals( 'Validation Status', $amp_post_type->label );
+		$this->assertEquals( false, $amp_post_type->public );
+		$this->assertTrue( $amp_post_type->show_ui );
+		$this->assertEquals( AMP_Options_Manager::OPTION_NAME, $amp_post_type->show_in_menu );
+		$this->assertTrue( $amp_post_type->show_in_admin_bar );
+	}
+
+	/**
+	 * Test for store_validation_errors()
+	 *
+	 * @covers AMP_Validation_Utils::store_validation_errors()
+	 */
+	public function test_store_validation_errors() {
+		global $post;
+		$post = $this->factory()->post->create_and_get(); // WPCS: global override ok.
+		add_theme_support( 'amp' );
+		AMP_Validation_Utils::process_markup( '<!--amp-source-stack {"type":"plugin","name":"foo"}-->' . $this->disallowed_tag . '<!--/amp-source-stack {"type":"plugin","name":"foo"}-->' );
+
+		$this->assertCount( 1, AMP_Validation_Utils::$validation_errors );
+		$this->assertEquals( 'script', AMP_Validation_Utils::$validation_errors[0]['node_name'] );
+		$this->assertEquals(
+			array(
+				'type' => 'plugin',
+				'name' => 'foo',
 			),
-			'removed_attributes' => null,
-			'processed_markup'   => $this->disallowed_tag,
+			AMP_Validation_Utils::$validation_errors[0]['sources'][0]
+		);
+
+		$url     = home_url( '/' );
+		$post_id = AMP_Validation_Utils::store_validation_errors( AMP_Validation_Utils::$validation_errors, $url );
+		$this->assertNotEmpty( $post_id );
+		$custom_post               = get_post( $post_id );
+		$validation                = AMP_Validation_Utils::summarize_validation_errors( json_decode( $custom_post->post_content, true ) );
+		$expected_removed_elements = array(
+			'script' => 1,
+		);
+		AMP_Validation_Utils::reset_validation_results();
+
+		// This should create a new post for the errors.
+		$this->assertEquals( AMP_Validation_Utils::POST_TYPE_SLUG, $custom_post->post_type );
+		$this->assertEquals( $expected_removed_elements, $validation[ AMP_Validation_Utils::REMOVED_ELEMENTS ] );
+		$this->assertEquals( array(), $validation[ AMP_Validation_Utils::REMOVED_ATTRIBUTES ] );
+		$this->assertEquals( array( 'foo' ), $validation[ AMP_Validation_Utils::SOURCES_INVALID_OUTPUT ]['plugin'] );
+		$meta = get_post_meta( $post_id, AMP_Validation_Utils::AMP_URL_META, true );
+		$this->assertEquals( $url, $meta );
+
+		AMP_Validation_Utils::reset_validation_results();
+		$url = home_url( '/?baz' );
+		AMP_Validation_Utils::process_markup( '<!--amp-source-stack {"type":"plugin","name":"foo"}-->' . $this->disallowed_tag . '<!--/amp-source-stack {"type":"plugin","name":"foo"}-->' );
+		$custom_post_id = AMP_Validation_Utils::store_validation_errors( AMP_Validation_Utils::$validation_errors, $url );
+		AMP_Validation_Utils::reset_validation_results();
+		$meta = get_post_meta( $post_id, AMP_Validation_Utils::AMP_URL_META, false );
+		// A post exists for these errors, so the URL should be stored in the 'additional URLs' meta data.
+		$this->assertEquals( $post_id, $custom_post_id );
+		$this->assertContains( $url, $meta );
+
+		$url = home_url( '/?foo-bar' );
+		AMP_Validation_Utils::process_markup( '<!--amp-source-stack {"type":"plugin","name":"foo"}-->' . $this->disallowed_tag . '<!--/amp-source-stack {"type":"plugin","name":"foo"}-->' );
+		$custom_post_id = AMP_Validation_Utils::store_validation_errors( AMP_Validation_Utils::$validation_errors, $url );
+		AMP_Validation_Utils::reset_validation_results();
+		$meta = get_post_meta( $post_id, AMP_Validation_Utils::AMP_URL_META, false );
+
+		// The URL should again be stored in the 'additional URLs' meta data.
+		$this->assertEquals( $post_id, $custom_post_id );
+		$this->assertContains( $url, $meta );
+
+		AMP_Validation_Utils::reset_validation_results();
+		AMP_Validation_Utils::process_markup( '<!--amp-source-stack {"type":"plugin","name":"foo"}--><nonexistent></nonexistent><!--/amp-source-stack {"type":"plugin","name":"foo"}-->' );
+		$custom_post_id = AMP_Validation_Utils::store_validation_errors( AMP_Validation_Utils::$validation_errors, $url );
+		AMP_Validation_Utils::reset_validation_results();
+		$error_post                = get_post( $custom_post_id );
+		$validation                = AMP_Validation_Utils::summarize_validation_errors( json_decode( $error_post->post_content, true ) );
+		$expected_removed_elements = array(
+			'nonexistent' => 1,
+		);
+
+		// A post already exists for this URL, so it should be updated.
+		$this->assertEquals( $expected_removed_elements, $validation[ AMP_Validation_Utils::REMOVED_ELEMENTS ] );
+		$this->assertEquals( array( 'foo' ), $validation[ AMP_Validation_Utils::SOURCES_INVALID_OUTPUT ]['plugin'] );
+		$this->assertContains( $url, get_post_meta( $custom_post_id, AMP_Validation_Utils::AMP_URL_META, false ) );
+
+		AMP_Validation_Utils::reset_validation_results();
+		AMP_Validation_Utils::process_markup( $this->valid_amp_img );
+
+		// There are no errors, so the existing error post should be deleted.
+		$custom_post_id = AMP_Validation_Utils::store_validation_errors( AMP_Validation_Utils::$validation_errors, $url );
+		AMP_Validation_Utils::reset_validation_results();
+
+		$this->assertNull( $custom_post_id );
+		remove_theme_support( 'amp' );
+	}
+
+	/**
+	 * Test for store_validation_errors() when existing post is trashed.
+	 *
+	 * @covers AMP_Validation_Utils::store_validation_errors()
+	 */
+	public function test_store_validation_errors_untrashing() {
+		$validation_errors = $this->get_mock_errors();
+
+		$first_post_id = AMP_Validation_Utils::store_validation_errors( $validation_errors, home_url( '/foo/' ) );
+		$this->assertInternalType( 'int', $first_post_id );
+
+		$post_name = get_post( $first_post_id )->post_name;
+		wp_trash_post( $first_post_id );
+		$this->assertEquals( $post_name . '__trashed', get_post( $first_post_id )->post_name );
+
+		$next_post_id = AMP_Validation_Utils::store_validation_errors( $validation_errors, home_url( '/bar/' ) );
+		$this->assertInternalType( 'int', $next_post_id );
+		$this->assertEquals( $post_name, get_post( $next_post_id )->post_name );
+		$this->assertEquals( $next_post_id, $first_post_id );
+
+		$this->assertEqualSets(
+			array(
+				home_url( '/foo/' ),
+				home_url( '/bar/' ),
+			),
+			get_post_meta( $next_post_id, AMP_Validation_Utils::AMP_URL_META, false )
+		);
+	}
+
+	/**
+	 * Test for get_validation_status_post().
+	 *
+	 * @covers AMP_Validation_Utils::get_validation_status_post()
+	 */
+	public function test_get_validation_status_post() {
+		global $post;
+		$post           = $this->factory()->post->create_and_get(); // WPCS: global override ok.
+		$custom_post_id = $this->factory()->post->create( array(
+			'post_type' => AMP_Validation_Utils::POST_TYPE_SLUG,
+		) );
+
+		$url = get_permalink( $custom_post_id );
+		$this->assertEquals( null, AMP_Validation_Utils::get_validation_status_post( $url ) );
+
+		update_post_meta( $custom_post_id, AMP_Validation_Utils::AMP_URL_META, $url );
+		$this->assertEquals( $custom_post_id, AMP_Validation_Utils::get_validation_status_post( $url )->ID );
+	}
+
+	/**
+	 * Test for validate_after_plugin_activation().
+	 *
+	 * @covers AMP_Validation_Utils::validate_after_plugin_activation()
+	 */
+	public function test_validate_after_plugin_activation() {
+		add_filter( 'amp_pre_get_permalink', '__return_empty_string' );
+		$r = AMP_Validation_Utils::validate_after_plugin_activation();
+		$this->assertInstanceOf( 'WP_Error', $r );
+		$this->assertEquals( 'no_published_post_url_available', $r->get_error_code() );
+		remove_filter( 'amp_pre_get_permalink', '__return_empty_string' );
+
+		$validation_errors = array(
+			array(
+				'code' => 'example',
+			),
+		);
+
+		$this->factory()->post->create();
+		$filter = function() use ( $validation_errors ) {
+			return array(
+				'body'    => '',
+				'headers' => array(
+					AMP_Validation_Utils::VALIDATION_ERRORS_RESPONSE_HEADER_NAME => wp_json_encode( $validation_errors ),
+				),
+			);
+		};
+		add_filter( 'pre_http_request', $filter, 10, 3 );
+		$r = AMP_Validation_Utils::validate_after_plugin_activation();
+		remove_filter( 'pre_http_request', $filter );
+		$this->assertEquals( $validation_errors, $r );
+		$this->assertEquals( $validation_errors, get_transient( AMP_Validation_Utils::PLUGIN_ACTIVATION_VALIDATION_ERRORS_TRANSIENT_KEY ) );
+	}
+
+	/**
+	 * Test for validate_url().
+	 *
+	 * @covers AMP_Validation_Utils::validate_url()
+	 */
+	public function test_validate_url() {
+		$validation_errors = array(
+			array(
+				'code' => 'example',
+			),
+		);
+
+		// Test headers absent.
+		$this->factory()->post->create();
+		$filter = function() use ( $validation_errors ) {
+			return array(
+				'body'    => '',
+				'headers' => array(),
+			);
+		};
+		add_filter( 'pre_http_request', $filter );
+		$r = AMP_Validation_Utils::validate_url( home_url( '/' ) );
+		$this->assertInstanceOf( 'WP_Error', $r );
+		$this->assertEquals( 'response_header_absent', $r->get_error_code() );
+		remove_filter( 'pre_http_request', $filter );
+
+		// Test success.
+		$that          = $this;
+		$validated_url = home_url( '/foo/' );
+		$filter        = function( $pre, $r, $url ) use ( $validation_errors, $validated_url, $that ) {
+			unset( $pre, $r );
+			$that->assertStringStartsWith(
+				add_query_arg(
+					AMP_Validation_Utils::VALIDATE_QUERY_VAR,
+					1,
+					$validated_url
+				),
+				$url
+			);
+			return array(
+				'body'    => '',
+				'headers' => array(
+					AMP_Validation_Utils::VALIDATION_ERRORS_RESPONSE_HEADER_NAME => wp_json_encode( $validation_errors ),
+				),
+			);
+		};
+		add_filter( 'pre_http_request', $filter, 10, 3 );
+		$r = AMP_Validation_Utils::validate_url( $validated_url );
+		$this->assertEquals( $validation_errors, $r );
+		remove_filter( 'pre_http_request', $filter );
+	}
+
+	/**
+	 * Test for plugin_notice()
+	 *
+	 * @covers AMP_Validation_Utils::plugin_notice()
+	 */
+	public function test_plugin_notice() {
+		global $pagenow;
+		ob_start();
+		AMP_Validation_Utils::plugin_notice();
+		$output = ob_get_clean();
+		$this->assertEmpty( $output );
+		$pagenow          = 'plugins.php'; // WPCS: global override ok.
+		$_GET['activate'] = 'true';
+
+		set_transient( AMP_Validation_Utils::PLUGIN_ACTIVATION_VALIDATION_ERRORS_TRANSIENT_KEY, array(
+			array(
+				'code'    => 'example',
+				'sources' => array(
+					array(
+						'type' => 'plugin',
+						'name' => 'foo-bar',
+					),
+				),
+			),
+		) );
+		ob_start();
+		AMP_Validation_Utils::plugin_notice();
+		$output = ob_get_clean();
+		$this->assertContains( 'Warning: The following plugin may be incompatible with AMP', $output );
+		$this->assertContains( $this->plugin_name, $output );
+		$this->assertContains( 'More details', $output );
+		$this->assertContains( admin_url( 'edit.php' ), $output );
+	}
+
+	/**
+	 * Test for add_post_columns()
+	 *
+	 * @covers AMP_Validation_Utils::add_post_columns()
+	 */
+	public function test_add_post_columns() {
+		$initial_columns = array(
+			'cb' => '<input type="checkbox">',
+		);
+		$this->assertEquals(
+			array_merge(
+				$initial_columns,
+				array(
+					'url_count'                            => 'Count',
+					AMP_Validation_Utils::REMOVED_ELEMENTS => 'Removed Elements',
+					AMP_Validation_Utils::REMOVED_ATTRIBUTES => 'Removed Attributes',
+					AMP_Validation_Utils::SOURCES_INVALID_OUTPUT => 'Incompatible Sources',
+				)
+			),
+			AMP_Validation_Utils::add_post_columns( $initial_columns )
 		);
-		$this->assertEquals( $expected_response, $response );
 	}
 
 	/**
-	 * Test reset_removed
+	 * Test for output_custom_column()
 	 *
-	 * @see AMP_Validation_Utils::reset_removed()
+	 * @dataProvider get_custom_columns
+	 * @covers AMP_Validation_Utils::output_custom_column()
+	 * @param string $column_name The name of the column.
+	 * @param string $expected_value The value that is expected to be present in the column markup.
 	 */
-	public function test_reset_removed() {
-		AMP_Validation_Utils::$removed_nodes[]    = $this->node;
-		AMP_Validation_Utils::$removed_attributes = array( 'onclick' );
-		AMP_Validation_Utils::reset_removed();
+	public function test_output_custom_column( $column_name, $expected_value ) {
+		ob_start();
+		AMP_Validation_Utils::output_custom_column( $column_name, $this->create_custom_post() );
+		$this->assertContains( $expected_value, ob_get_clean() );
+	}
 
-		$this->assertEquals( null, AMP_Validation_Utils::$removed_nodes );
-		$this->assertEquals( null, AMP_Validation_Utils::$removed_attributes );
+	/**
+	 * Gets the test data for test_output_custom_column().
+	 *
+	 * @return array $columns
+	 */
+	public function get_custom_columns() {
+		return array(
+			'url_count'             => array(
+				'url_count',
+				'1',
+			),
+			'invalid_element'       => array(
+				AMP_Validation_Utils::REMOVED_ELEMENTS,
+				$this->disallowed_tag_name,
+			),
+			'removed_attributes'    => array(
+				AMP_Validation_Utils::REMOVED_ATTRIBUTES,
+				$this->disallowed_attribute_name,
+			),
+			'sources_invalid_input' => array(
+				AMP_Validation_Utils::SOURCES_INVALID_OUTPUT,
+				$this->plugin_name,
+			),
+		);
 	}
 
 	/**
-	 * Test validate_arg
+	 * Test for filter_row_actions()
 	 *
-	 * @see AMP_Validation_Utils::validate_arg()
+	 * @covers AMP_Validation_Utils::filter_row_actions()
 	 */
-	public function test_validate_arg() {
-		$invalid_number = 54321;
-		$invalid_array  = array( 'foo', 'bar' );
-		$valid_string   = '<div class="baz"></div>';
-		$this->assertFalse( AMP_Validation_Utils::validate_arg( $invalid_number ) );
-		$this->assertFalse( AMP_Validation_Utils::validate_arg( $invalid_array ) );
-		$this->assertTrue( AMP_Validation_Utils::validate_arg( $valid_string ) );
+	public function test_filter_row_actions() {
+		$this->set_capability();
+
+		$initial_actions = array(
+			'trash' => '<a href="https://example.com">Trash</a>',
+		);
+		$post            = $this->factory()->post->create_and_get();
+		$this->assertEquals( $initial_actions, AMP_Validation_Utils::filter_row_actions( $initial_actions, $post ) );
+
+		$custom_post_id = $this->create_custom_post();
+		$actions        = AMP_Validation_Utils::filter_row_actions( $initial_actions, get_post( $custom_post_id ) );
+		$url            = get_post_meta( $custom_post_id, AMP_Validation_Utils::AMP_URL_META, true );
+		$this->assertContains( $url, $actions[ AMP_Validation_Utils::RECHECK_ACTION ] );
+		$this->assertEquals( $initial_actions['trash'], $actions['trash'] );
 	}
 
 	/**
-	 * Test is_authorized
+	 * Test for add_bulk_action()
 	 *
-	 * @see AMP_Validation_Utils::is_authorized()
+	 * @covers AMP_Validation_Utils::add_bulk_action()
 	 */
-	public function test_is_authorized() {
-		$this->assertFalse( AMP_Validation_Utils::is_authorized() );
-		$this->set_authorized();
-		$this->assertTrue( AMP_Validation_Utils::is_authorized() );
+	public function test_add_bulk_action() {
+		$initial_action = array(
+			'edit' => 'Edit',
+		);
+		$actions        = AMP_Validation_Utils::add_bulk_action( $initial_action );
+		$this->assertFalse( isset( $action['edit'] ) );
+		$this->assertEquals( 'Recheck', $actions[ AMP_Validation_Utils::RECHECK_ACTION ] );
 	}
 
 	/**
-	 * Test error_message().
+	 * Test for handle_bulk_action()
 	 *
-	 * @see AMP_Validation_Utils::error_message().
+	 * @covers AMP_Validation_Utils::handle_bulk_action()
 	 */
-	public function test_error_message() {
-		$url            = 'https://example.org/am';
-		$with_query_arg = wp_parse_url( AMP_Validation_Utils::error_message( $url ) );
-		$this->assertContains( AMP_Validation_Utils::ERROR_QUERY_KEY, $with_query_arg['query'] );
-		$this->assertContains( AMP_Validation_Utils::ERROR_QUERY_VALUE, $with_query_arg['query'] );
+	public function test_handle_bulk_action() {
+		$initial_redirect                          = admin_url( 'plugins.php' );
+		$items                                     = array( $this->create_custom_post() );
+		$urls_tested                               = '1';
+		$_GET[ AMP_Validation_Utils::URLS_TESTED ] = $urls_tested;
+
+		// The action isn't correct, so the callback should return the URL unchanged.
+		$this->assertEquals( $initial_redirect, AMP_Validation_Utils::handle_bulk_action( $initial_redirect, 'trash', $items ) );
+
+		$that   = $this;
+		$filter = function() use ( $that ) {
+			return array(
+				'body'    => '',
+				'headers' => array(
+					AMP_Validation_Utils::VALIDATION_ERRORS_RESPONSE_HEADER_NAME => wp_json_encode( $that->get_mock_errors() ),
+				),
+			);
+		};
+		add_filter( 'pre_http_request', $filter, 10, 3 );
+		$this->assertEquals(
+			add_query_arg(
+				array(
+					AMP_Validation_Utils::URLS_TESTED      => $urls_tested,
+					AMP_Validation_Utils::REMAINING_ERRORS => count( $items ),
+				),
+				$initial_redirect
+			),
+			AMP_Validation_Utils::handle_bulk_action( $initial_redirect, AMP_Validation_Utils::RECHECK_ACTION, $items )
+		);
+		remove_filter( 'pre_http_request', $filter, 10, 3 );
 	}
 
 	/**
-	 * Test display_error().
+	 * Test for remaining_error_notice()
 	 *
-	 * @see AMP_Validation_Utils::display_error().
+	 * @covers AMP_Validation_Utils::remaining_error_notice()
 	 */
-	public function test_display_error() {
+	public function test_remaining_error_notice() {
+		ob_start();
+		AMP_Validation_Utils::remaining_error_notice();
+		$this->assertEmpty( ob_get_clean() );
+
+		$_GET['post_type'] = 'post';
+		ob_start();
+		AMP_Validation_Utils::remaining_error_notice();
+		$this->assertEmpty( ob_get_clean() );
+
+		set_current_screen( 'edit.php' );
+		get_current_screen()->post_type = AMP_Validation_Utils::POST_TYPE_SLUG;
+
+		$_GET[ AMP_Validation_Utils::REMAINING_ERRORS ] = '1';
+		$_GET[ AMP_Validation_Utils::URLS_TESTED ]      = '1';
+		ob_start();
+		AMP_Validation_Utils::remaining_error_notice();
+		$this->assertContains( 'The rechecked URL still has validation errors', ob_get_clean() );
+
+		$_GET[ AMP_Validation_Utils::URLS_TESTED ] = '2';
+		ob_start();
+		AMP_Validation_Utils::remaining_error_notice();
+		$this->assertContains( 'The rechecked URLs still have validation errors', ob_get_clean() );
+
+		$_GET[ AMP_Validation_Utils::REMAINING_ERRORS ] = '0';
+		ob_start();
+		AMP_Validation_Utils::remaining_error_notice();
+		$this->assertContains( 'The rechecked URLs have no validation error', ob_get_clean() );
+
+		$_GET[ AMP_Validation_Utils::URLS_TESTED ] = '1';
+		ob_start();
+		AMP_Validation_Utils::remaining_error_notice();
+		$this->assertContains( 'The rechecked URL has no validation error', ob_get_clean() );
+
+		unset( $GLOBALS['current_screen'] );
+	}
+
+	/**
+	 * Test for handle_inline_recheck()
+	 *
+	 * @covers AMP_Validation_Utils::handle_inline_recheck()
+	 */
+	public function test_handle_inline_recheck() {
+		$post_id              = $this->create_custom_post();
+		$_REQUEST['_wpnonce'] = wp_create_nonce( AMP_Validation_Utils::NONCE_ACTION . $post_id );
 		wp_set_current_user( $this->factory()->user->create( array(
 			'role' => 'administrator',
 		) ) );
-		unset( $_GET[ AMP_Validation_Utils::ERROR_QUERY_KEY ] );
+
+		try {
+			AMP_Validation_Utils::handle_inline_recheck( $post_id );
+		} catch ( WPDieException $e ) {
+			$exception = $e;
+		}
+
+		// This calls wp_redirect(), which throws an exception.
+		$this->assertTrue( isset( $exception ) );
+	}
+
+	/**
+	 * Test for remove_publish_meta_box()
+	 *
+	 * @covers AMP_Validation_Utils::remove_publish_meta_box()
+	 */
+	public function test_remove_publish_meta_box() {
+		global $wp_meta_boxes;
+		AMP_Validation_Utils::remove_publish_meta_box();
+		$contexts = $wp_meta_boxes[ AMP_Validation_Utils::POST_TYPE_SLUG ]['side'];
+		foreach ( $contexts as $context ) {
+			$this->assertFalse( $context['submitdiv'] );
+		}
+	}
+
+	/**
+	 * Test for add_meta_boxes()
+	 *
+	 * @covers AMP_Validation_Utils::add_meta_boxes()
+	 */
+	public function test_add_meta_boxes() {
+		global $wp_meta_boxes;
+		AMP_Validation_Utils::add_meta_boxes();
+		$side_meta_box = $wp_meta_boxes[ AMP_Validation_Utils::POST_TYPE_SLUG ]['side']['default'][ AMP_Validation_Utils::STATUS_META_BOX ];
+		$this->assertEquals( AMP_Validation_Utils::STATUS_META_BOX, $side_meta_box['id'] );
+		$this->assertEquals( 'Status', $side_meta_box['title'] );
+		$this->assertEquals(
+			array(
+				self::TESTED_CLASS,
+				'print_status_meta_box',
+			),
+			$side_meta_box['callback']
+		);
+
+		$full_meta_box = $wp_meta_boxes[ AMP_Validation_Utils::POST_TYPE_SLUG ]['normal']['default'][ AMP_Validation_Utils::VALIDATION_ERRORS_META_BOX ];
+		$this->assertEquals( AMP_Validation_Utils::VALIDATION_ERRORS_META_BOX, $full_meta_box['id'] );
+		$this->assertEquals( 'Validation Errors', $full_meta_box['title'] );
+		$this->assertEquals(
+			array(
+				self::TESTED_CLASS,
+				'print_validation_errors_meta_box',
+			),
+			$full_meta_box['callback']
+		);
+	}
+
+	/**
+	 * Test for print_status_meta_box()
+	 *
+	 * @covers AMP_Validation_Utils::print_status_meta_box()
+	 */
+	public function test_print_status_meta_box() {
+		$this->set_capability();
+		$post_storing_error = get_post( $this->create_custom_post() );
+		$url                = get_post_meta( $post_storing_error->ID, AMP_Validation_Utils::AMP_URL_META, true );
+		$post_with_error    = AMP_Validation_Utils::get_validation_status_post( $url );
 		ob_start();
-		AMP_Validation_Utils::display_error();
+		AMP_Validation_Utils::print_status_meta_box( $post_storing_error );
 		$output = ob_get_clean();
-		$this->assertFalse( strpos( $output, 'notice notice-error' ) );
-		$this->assertFalse( strpos( $output, 'Notice: your post fails AMP validation' ) );
 
-		$_GET[ AMP_Validation_Utils::ERROR_QUERY_KEY ] = AMP_Validation_Utils::ERROR_QUERY_VALUE;
-		$_REQUEST[ AMP_Validation_Utils::ERROR_NONCE ] = wp_create_nonce( AMP_Validation_Utils::ERROR_NONCE_ACTION );
-		$_REQUEST['_wp_http_referer']                  = admin_url();
+		$this->assertContains( date_i18n( 'M j, Y @ H:i', strtotime( $post_with_error->post_date ) ), $output );
+		$this->assertContains( 'Published on:', $output );
+		$this->assertContains( 'Move to Trash', $output );
+		$this->assertContains( esc_url( get_delete_post_link( $post_storing_error->ID ) ), $output );
+		$this->assertContains( 'misc-pub-section', $output );
+		$this->assertContains(
+			AMP_Validation_Utils::get_recheck_link(
+				$post_with_error,
+				add_query_arg(
+					'post',
+					$post_with_error->ID,
+					admin_url( 'post.php' )
+				)
+			),
+			$output
+		);
+	}
+
+	/**
+	 * Test for print_status_meta_box()
+	 *
+	 * @covers AMP_Validation_Utils::print_status_meta_box()
+	 */
+	public function test_print_validation_errors_meta_box() {
+		$this->set_capability();
+		$post_storing_error     = get_post( $this->create_custom_post() );
+		$first_url              = get_post_meta( $post_storing_error->ID, AMP_Validation_Utils::AMP_URL_META, true );
+		$second_url_same_errors = get_permalink( $this->factory()->post->create() );
+		AMP_Validation_Utils::store_validation_errors( $this->get_mock_errors(), $second_url_same_errors );
 		ob_start();
-		AMP_Validation_Utils::display_error();
+		AMP_Validation_Utils::print_validation_errors_meta_box( $post_storing_error );
 		$output = ob_get_clean();
-		$this->assertContains( 'notice notice-warning', $output );
-		$this->assertContains( 'Warning:', $output );
+
+		$this->assertContains( '<details', $output );
+		$this->assertContains( $this->disallowed_tag_name, $output );
+		$this->assertContains( $this->disallowed_attribute_name, $output );
+		$this->assertContains( 'URLs', $output );
+		$this->assertContains( $first_url, $output );
+		$this->assertContains( $second_url_same_errors, $output );
+		AMP_Validation_Utils::reset_validation_results();
 	}
 
 	/**
-	 * Add a nonce to the $_REQUEST, so that is_authorized() returns true.
+	 * Test for get_debug_url()
 	 *
-	 * @return void.
+	 * @covers AMP_Validation_Utils::get_debug_url()
 	 */
-	public function set_authorized() {
-		global $_REQUEST, $post; // WPCS: CSRF ok.
-		if ( ! AMP_Validation_Utils::has_cap() ) {
-			wp_set_current_user( $this->factory()->user->create( array(
-				'role' => 'administrator',
-			) ) );
-		}
-		$post_id              = $this->factory()->post->create();
-		$post                 = get_post( $post_id ); // WPCS: global override ok.
-		$_REQUEST['_wpnonce'] = wp_create_nonce( 'update-post_' . $post_id ); // WPCS: global override ok.
+	public function test_get_debug_url() {
+		$this->assertContains( AMP_Validation_Utils::VALIDATE_QUERY_VAR . '=1', AMP_Validation_Utils::get_debug_url( 'https://example.com/foo/' ) );
+		$this->assertContains( AMP_Validation_Utils::DEBUG_QUERY_VAR . '=1', AMP_Validation_Utils::get_debug_url( 'https://example.com/foo/' ) );
+		$this->assertStringEndsWith( '#development=1', AMP_Validation_Utils::get_debug_url( 'https://example.com/foo/' ) );
+	}
+
+	/**
+	 * Test for get_recheck_link()
+	 *
+	 * @covers AMP_Validation_Utils::get_recheck_link()
+	 */
+	public function test_get_recheck_link() {
+		$this->set_capability();
+		$post_id = $this->create_custom_post();
+		$url     = get_edit_post_link( $post_id, 'raw' );
+		$link    = AMP_Validation_Utils::get_recheck_link( get_post( $post_id ), $url );
+		$this->assertContains( AMP_Validation_Utils::RECHECK_ACTION, $link );
+		$this->assertContains( wp_create_nonce( AMP_Validation_Utils::NONCE_ACTION . $post_id ), $link );
+		$this->assertContains( 'Recheck the URL for AMP validity', $link );
+	}
+
+	/**
+	 * Creates and inserts a custom post.
+	 *
+	 * @return int|WP_Error $error_post The ID of new custom post, or an error.
+	 */
+	public function create_custom_post() {
+		$content        = wp_json_encode( $this->get_mock_errors() );
+		$encoded_errors = md5( $content );
+		$post_args      = array(
+			'post_type'    => AMP_Validation_Utils::POST_TYPE_SLUG,
+			'post_name'    => $encoded_errors,
+			'post_content' => $content,
+			'post_status'  => 'publish',
+		);
+		$error_post     = wp_insert_post( wp_slash( $post_args ) );
+		$url            = home_url( '/' );
+		update_post_meta( $error_post, AMP_Validation_Utils::AMP_URL_META, $url );
+		return $error_post;
+	}
+
+	/**
+	 * Gets mock errors for tests.
+	 *
+	 * @return array $errors[][] {
+	 *     The data of the validation errors.
+	 *
+	 *     @type string    $code        Error code.
+	 *     @type string    $node_name   Name of removed node.
+	 *     @type string    $parent_name Name of parent node.
+	 *     @type array[][] $sources     Source data, including plugins and themes.
+	 * }
+	 */
+	public function get_mock_errors() {
+		return array(
+			array(
+				'code'            => AMP_Validation_Utils::INVALID_ELEMENT_CODE,
+				'node_name'       => $this->disallowed_tag_name,
+				'parent_name'     => 'div',
+				'node_attributes' => array(),
+				'sources'         => array(
+					array(
+						'type' => 'plugin',
+						'name' => $this->plugin_name,
+					),
+				),
+			),
+			array(
+				'code'               => AMP_Validation_Utils::INVALID_ATTRIBUTE_CODE,
+				'node_name'          => $this->disallowed_attribute_name,
+				'parent_name'        => 'div',
+				'element_attributes' => array(
+					$this->disallowed_attribute_name => '',
+				),
+				'sources'            => array(
+					array(
+						'type' => 'plugin',
+						'name' => $this->plugin_name,
+					),
+				),
+			),
+		);
 	}
 
 }
diff --git a/tests/test-tag-and-attribute-sanitizer.php b/tests/test-tag-and-attribute-sanitizer.php
index 1549a5c23bd..5d30dca97f4 100644
--- a/tests/test-tag-and-attribute-sanitizer.php
+++ b/tests/test-tag-and-attribute-sanitizer.php
@@ -165,6 +165,36 @@ public function get_body_data() {
 				array( 'amp-izlesene' ),
 			),
 
+			'amp-mathml'                                                => array(
+				'<amp-mathml layout="container" inline data-formula="\[x = {-b \pm \sqrt{b^2-4ac} \over 2a}.\]"></amp-mathml>',
+				null, // No change.
+				array( 'amp-mathml' ),
+			),
+
+			'amp-riddle-quiz'                                           => array(
+				'<amp-riddle-quiz layout="responsive" width="600" height="400" data-riddle-id="25799"></amp-riddle-quiz>',
+				null, // No change.
+				array( 'amp-riddle-quiz' ),
+			),
+
+			'amp-wistia-player'                                         => array(
+				'<amp-wistia-player data-media-hashed-id="u8p9wq6mq8" width="512" height="360"></amp-wistia-player>',
+				null, // No change.
+				array( 'amp-wistia-player' ),
+			),
+
+			'amp-byside-content'                                        => array(
+				'<amp-byside-content data-webcare-id="D6604AE5D0" data-channel="" data-lang="pt" data-fid="" data-label="amp-number" layout="fixed" width="120" height="40"></amp-byside-content>',
+				null, // No change.
+				array( 'amp-byside-content' ),
+			),
+
+			'amp-bind-macro'                                            => array(
+				'<amp-bind-macro id="circleArea" arguments="radius" expression="3.14 * radius * radius"></amp-bind-macro>',
+				null, // No change.
+				array( 'amp-bind' ),
+			),
+
 			'amp-nexxtv-player'                                         => array(
 				'<amp-nexxtv-player data-mediaid="123ABC" data-client="4321"></amp-nexxtv-player>',
 				null, // No change.
@@ -650,6 +680,23 @@ public function get_body_data() {
 				'<a class="foo" href="">value</a>',
 			),
 
+			'a_with_wrong_host'                                         => array(
+				'<a class="foo" href="http://foo bar">value</a>',
+				'<a class="foo" href="">value</a>',
+			),
+			'a_with_encoded_host'                                       => array(
+				'<a class="foo" href="http://%65%78%61%6d%70%6c%65%2e%63%6f%6d/foo/">value</a>',
+				null,
+			),
+			'a_with_wrong_schemeless_host'                              => array(
+				'<a class="foo" href="//bad domain with a space.com/foo">value</a>',
+				'<a class="foo" href="">value</a>',
+			),
+			'a_with_mail_host'                                          => array(
+				'<a class="foo" href="mail to:foo@bar.com">value</a>',
+				'<a class="foo" href="">value</a>',
+			),
+
 			// font is removed so we should check that other elements are checked as well.
 			'font_with_other_bad_elements'                              => array(
 				'<font size="1">Headline</font><span style="color: blue">Span</span>',
@@ -674,6 +721,24 @@ public function get_body_data() {
 				null, // No change.
 				array( 'amp-selector', 'amp-form', 'amp-carousel' ),
 			),
+
+			'amp_live_list_sort'                                        => array(
+				'<amp-live-list sort="ascending" data-poll-interval="15000" data-max-items-per-page="5" id="amp-live-list-insert-blog"><button update on="tap:amp-live-list-insert-blog.update" class="ampstart-btn ml1 caps">You have updates</button><div items><div id="A green landscape with trees." data-sort-time="20180317225019">Hello</div></div></amp-live-list>',
+				null, // No change.
+				array( 'amp-live-list' ),
+			),
+
+			'amp_consent'                                               => array(
+				'<amp-consent media="all" noloading></amp-consent>',
+				null, // No change.
+				array( 'amp-consent' ),
+			),
+
+			'amp_date_picker'                                           => array(
+				'<amp-date-picker id="simple-date-picker" type="single" mode="overlay" layout="container" on="select:AMP.setState({date1: event.date, dateType1: event.id})" format="Y-MM-DD" open-after-select input-selector="[name=date1]" class="mr1 ml1 flex picker"><div class="ampstart-input inline-block mt1"><input class="border-none p0" name="date1" placeholder="Pick a date"></div><button class="ampstart-btn m1 caps" on="tap: simple-date-picker.clear">Clear</button></amp-date-picker>',
+				null, // No change.
+				array( 'amp-date-picker' ),
+			),
 		);
 	}
 
diff --git a/wpcom-helper.php b/wpcom-helper.php
index 37af6a9ee91..05e9bc8b175 100644
--- a/wpcom-helper.php
+++ b/wpcom-helper.php
@@ -1,17 +1,22 @@
 <?php
+/**
+ * WPCOM-specific things.
+ *
+ * @todo Move this into Jetpack. See https://github.com/Automattic/amp-wp/issues/1021
+ * @package AMP
+ */
 
-// WPCOM-specific things
 add_action( 'pre_amp_render_post', 'jetpack_amp_disable_the_content_filters' );
 
-// Disable admin menu
+// Disable admin menu.
 add_filter( 'amp_options_menu_is_enabled', '__return_false', 9999 );
 
 /**
  * Disable the_content filters for Jetpack.
  *
- * @param int $post_id Post ID.
+ * @since 0.3
  */
-function jetpack_amp_disable_the_content_filters( $post_id ) {
+function jetpack_amp_disable_the_content_filters() {
 	add_filter( 'post_flair_disable', '__return_true', 99 );
 	add_filter( 'videopress_show_2015_player', '__return_true' );
 	add_filter( 'protected_embeds_use_form_post', '__return_false' );
@@ -24,7 +29,12 @@ function jetpack_amp_disable_the_content_filters( $post_id ) {
 
 add_action( 'amp_post_template_head', 'jetpack_amp_add_og_tags' );
 
-function jetpack_amp_add_og_tags( $amp_template ) {
+/**
+ * Add Open Graph tags.
+ *
+ * @since 0.3
+ */
+function jetpack_amp_add_og_tags() {
 	if ( function_exists( 'jetpack_og_tags' ) ) {
 		jetpack_og_tags();
 	}
@@ -32,9 +42,18 @@ function jetpack_amp_add_og_tags( $amp_template ) {
 
 add_filter( 'amp_post_template_metadata', 'jetpack_amp_post_template_metadata', 10, 2 );
 
+/**
+ * Add publisher and image metadata.
+ *
+ * @since 0.3
+ *
+ * @param array   $metadata Metadata array.
+ * @param WP_Post $post     Post.
+ * @return array Modified metadata array.
+ */
 function jetpack_amp_post_template_metadata( $metadata, $post ) {
 	if ( isset( $metadata['publisher'] ) && ! isset( $metadata['publisher']['logo'] ) ) {
-		$metadata = wpcom_amp_add_blavatar_to_metadata( $metadata, $post );
+		$metadata = wpcom_amp_add_blavatar_to_metadata( $metadata );
 	}
 
 	if ( ! isset( $metadata['image'] ) ) {
@@ -44,22 +63,40 @@ function jetpack_amp_post_template_metadata( $metadata, $post ) {
 	return $metadata;
 }
 
-function wpcom_amp_add_blavatar_to_metadata( $metadata, $post ) {
+/**
+ * Add blavatar to metadata.
+ *
+ * @since 0.3
+ *
+ * @param array $metadata Metadata.
+ * @return array Metadata.
+ */
+function wpcom_amp_add_blavatar_to_metadata( $metadata ) {
 	if ( ! function_exists( 'blavatar_domain' ) ) {
 		return $metadata;
 	}
 
 	$size = 60;
+
 	$metadata['publisher']['logo'] = array(
-		'@type' => 'ImageObject',
-		'url' => blavatar_url( blavatar_domain( site_url() ), 'img', $size, staticize_subdomain( 'https://wordpress.com/i/favicons/apple-touch-icon-60x60.png' ) ),
-		'width' => $size,
+		'@type'  => 'ImageObject',
+		'url'    => blavatar_url( blavatar_domain( site_url() ), 'img', $size, staticize_subdomain( 'https://wordpress.com/i/favicons/apple-touch-icon-60x60.png' ) ),
+		'width'  => $size,
 		'height' => $size,
 	);
 
 	return $metadata;
 }
 
+/**
+ * Add image to metadata.
+ *
+ * @since 0.3.2
+ *
+ * @param array   $metadata Metadata.
+ * @param WP_Post $post     Post.
+ * @return array Metadata.
+ */
 function wpcom_amp_add_image_to_metadata( $metadata, $post ) {
 	if ( ! class_exists( 'Jetpack_PostImages' ) ) {
 		return wpcom_amp_add_fallback_image_to_metadata( $metadata );
@@ -67,10 +104,10 @@ function wpcom_amp_add_image_to_metadata( $metadata, $post ) {
 
 	$image = Jetpack_PostImages::get_image( $post->ID, array(
 		'fallback_to_avatars' => true,
-		'avatar_size' => 200,
-		// AMP already attempts these
-		'from_thumbnail' => false,
-		'from_attachment' => false,
+		'avatar_size'         => 200,
+		// AMP already attempts these.
+		'from_thumbnail'      => false,
+		'from_attachment'     => false,
 	) );
 
 	if ( empty( $image ) ) {
@@ -80,30 +117,37 @@ function wpcom_amp_add_image_to_metadata( $metadata, $post ) {
 	if ( ! isset( $image['src_width'] ) ) {
 		$dimensions = wpcom_amp_extract_image_dimensions_from_getimagesize( array(
 			$image['src'] => false,
-			)
-		);
+		) );
 
 		if ( false !== $dimensions[ $image['src'] ] ) {
-			$image['src_width'] = $dimensions['width'];
+			$image['src_width']  = $dimensions['width'];
 			$image['src_height'] = $dimensions['height'];
 		}
 	}
 
 	$metadata['image'] = array(
-		'@type' => 'ImageObject',
-		'url' => $image['src'],
-		'width' => $image['src_width'],
+		'@type'  => 'ImageObject',
+		'url'    => $image['src'],
+		'width'  => $image['src_width'],
 		'height' => $image['src_height'],
 	);
 
 	return $metadata;
 }
 
+/**
+ * Add fallback image to metadata.
+ *
+ * @since 0.3.2
+ *
+ * @param array $metadata Metadata.
+ * @return array Metadata.
+ */
 function wpcom_amp_add_fallback_image_to_metadata( $metadata ) {
 	$metadata['image'] = array(
-		'@type' => 'ImageObject',
-		'url' => staticize_subdomain( 'https://wordpress.com/i/blank.jpg' ),
-		'width' => 200,
+		'@type'  => 'ImageObject',
+		'url'    => staticize_subdomain( 'https://wordpress.com/i/blank.jpg' ),
+		'width'  => 200,
 		'height' => 200,
 	);
 
@@ -111,36 +155,50 @@ function wpcom_amp_add_fallback_image_to_metadata( $metadata ) {
 }
 
 add_action( 'amp_extract_image_dimensions_batch_callbacks_registered', 'wpcom_amp_extract_image_dimensions_batch_add_custom_callbacks' );
+
+/**
+ * Add hooks to extract image dimensions.
+ *
+ * @since 0.5
+ */
 function wpcom_amp_extract_image_dimensions_batch_add_custom_callbacks() {
 	// If images are being served from Photon or WP.com files, try extracting the size using querystring.
 	add_action( 'amp_extract_image_dimensions_batch', 'wpcom_amp_extract_image_dimensions_from_querystring', 9, 1 ); // Hook in before the default extractors.
 
 	// Uses a special wpcom lib (wpcom_getimagesize) to extract dimensions as a last resort if we weren't able to figure them out.
-	add_action( 'amp_extract_image_dimensions_batch', 'wpcom_amp_extract_image_dimensions_from_getimagesize', 99, 1 ); // Our last resort, so run late
+	add_action( 'amp_extract_image_dimensions_batch', 'wpcom_amp_extract_image_dimensions_from_getimagesize', 99, 1 ); // Our last resort, so run late.
 
 	// The wpcom override obviates this one, so take it out.
-	remove_filter( 'amp_extract_image_dimensions_batch', array( 'AMP_Image_Dimension_Extractor', 'extract_by_downloading_images' ), 999, 1 );
+	remove_filter( 'amp_extract_image_dimensions_batch', array( 'AMP_Image_Dimension_Extractor', 'extract_by_downloading_images' ), 999 );
 }
 
+/**
+ * Extract image dimensions from query string.
+ *
+ * @since 0.5
+ *
+ * @param array $dimensions Dimensions.
+ * @return array Dimensions.
+ */
 function wpcom_amp_extract_image_dimensions_from_querystring( $dimensions ) {
-	foreach ( $dimensions as $url => $value  ) {
+	foreach ( $dimensions as $url => $value ) {
 
 		if ( is_array( $value ) ) {
 			continue;
 		}
 
-		$host = parse_url( $url, PHP_URL_HOST );
-		if ( ! wp_endswith( $host, '.wp.com' ) || ! wp_endswith( $host, '.files.wordpress.com' ) ) {
+		$host = wp_parse_url( $url, PHP_URL_HOST );
+		if ( ! wp_endswith( $host, '.wp.com' ) && ! wp_endswith( $host, '.files.wordpress.com' ) ) {
 			continue;
 		}
 
-		parse_str( parse_url( $url, PHP_URL_QUERY ), $query );
+		parse_str( wp_parse_url( $url, PHP_URL_QUERY ), $query );
 		$w = isset( $query['w'] ) ? absint( $query['w'] ) : false;
 		$h = isset( $query['h'] ) ? absint( $query['h'] ) : false;
 
 		if ( false !== $w && false !== $h ) {
 			$dimensions[ $url ] = array(
-				'width' => $w,
+				'width'  => $w,
 				'height' => $h,
 			);
 		}
@@ -148,6 +206,14 @@ function wpcom_amp_extract_image_dimensions_from_querystring( $dimensions ) {
 	return $dimensions;
 }
 
+/**
+ * Extract image dimensions via wpcom/imagesize.
+ *
+ * @since 0.5
+ *
+ * @param array $dimensions Dimensions.
+ * @return array Dimensions.
+ */
 function wpcom_amp_extract_image_dimensions_from_getimagesize( $dimensions ) {
 	if ( ! function_exists( 'require_lib' ) ) {
 		return $dimensions;
@@ -161,7 +227,7 @@ function wpcom_amp_extract_image_dimensions_from_getimagesize( $dimensions ) {
 		$result = wpcom_getimagesize( $url );
 		if ( is_array( $result ) ) {
 			$dimensions[ $url ] = array(
-				'width' => $result[0],
+				'width'  => $result[0],
 				'height' => $result[1],
 			);
 		}