diff --git a/.eslintrc.js b/.eslintrc.js
index de87304061990..583b71b3ffac5 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -564,32 +564,6 @@ module.exports = {
     },
     {
       files: [
-        "toolkit/content/tests/chrome/frame_popup_anchor.xhtml",
-        "toolkit/content/tests/chrome/frame_subframe_origin_subframe1.xhtml",
-        "toolkit/content/tests/chrome/frame_subframe_origin_subframe2.xhtml",
-        "toolkit/content/tests/chrome/test_arrowpanel.xhtml",
-        "toolkit/content/tests/chrome/test_autocomplete2.xhtml",
-        "toolkit/content/tests/chrome/test_autocomplete3.xhtml",
-        "toolkit/content/tests/chrome/test_autocomplete4.xhtml",
-        "toolkit/content/tests/chrome/test_autocomplete5.xhtml",
-        "toolkit/content/tests/chrome/test_autocomplete_emphasis.xhtml",
-        "toolkit/content/tests/chrome/test_autocomplete_mac_caret.xhtml",
-        "toolkit/content/tests/chrome/test_autocomplete_placehold_last_complete.xhtml",
-        "toolkit/content/tests/chrome/test_browser_drop.xhtml",
-        "toolkit/content/tests/chrome/test_bug1048178.xhtml",
-        "toolkit/content/tests/chrome/test_bug382990.xhtml",
-        "toolkit/content/tests/chrome/test_bug437844.xhtml",
-        "toolkit/content/tests/chrome/test_bug624329.xhtml",
-        "toolkit/content/tests/chrome/test_bug792324.xhtml",
-        "toolkit/content/tests/chrome/test_contextmenu_list.xhtml",
-        "toolkit/content/tests/chrome/test_cursorsnap.xhtml",
-        "toolkit/content/tests/chrome/test_dialogfocus.xhtml",
-        "toolkit/content/tests/chrome/test_hiddenitems.xhtml",
-        "toolkit/content/tests/chrome/test_hiddenpaging.xhtml",
-        "toolkit/content/tests/chrome/test_maximized_persist.xhtml",
-        "toolkit/content/tests/chrome/test_menu.xhtml",
-        "toolkit/content/tests/chrome/test_menuitem_blink.xhtml",
-        "toolkit/content/tests/chrome/test_menulist.xhtml",
         "toolkit/content/tests/chrome/test_menulist_keynav.xhtml",
         "toolkit/content/tests/chrome/test_mousescroll.xhtml",
         "toolkit/content/tests/chrome/test_mozinputbox_dictionary.xhtml",
diff --git a/toolkit/content/tests/chrome/frame_popup_anchor.xhtml b/toolkit/content/tests/chrome/frame_popup_anchor.xhtml
index df52936c06c02..142bc7b0af746 100644
--- a/toolkit/content/tests/chrome/frame_popup_anchor.xhtml
+++ b/toolkit/content/tests/chrome/frame_popup_anchor.xhtml
@@ -35,13 +35,13 @@ function popupShown()
   var left, top;
   var popuprect = document.getElementById("popup").getBoundingClientRect();
   if (isSecondTest) {
-    var buttonrect = document.getElementById("button").getBoundingClientRect();
+    let buttonrect = document.getElementById("button").getBoundingClientRect();
     left = buttonrect.left + 6;
     top = buttonrect.top + 6;
   }
   else {
-    var iframerect = parent.document.getElementById("frame").getBoundingClientRect();
-    var buttonrect = parent.document.getElementById("outerbutton").getBoundingClientRect();
+    let iframerect = parent.document.getElementById("frame").getBoundingClientRect();
+    let buttonrect = parent.document.getElementById("outerbutton").getBoundingClientRect();
 
     // The popup should appear anchored on the bottom left edge of the button, however
     // the client rectangle is relative to the iframe's document. Thus the coordinates
diff --git a/toolkit/content/tests/chrome/frame_subframe_origin_subframe1.xhtml b/toolkit/content/tests/chrome/frame_subframe_origin_subframe1.xhtml
index 4b57303e75178..f68a06d85d516 100644
--- a/toolkit/content/tests/chrome/frame_subframe_origin_subframe1.xhtml
+++ b/toolkit/content/tests/chrome/frame_subframe_origin_subframe1.xhtml
@@ -27,7 +27,6 @@ function runTests()
 
 function mouseMove(e) {
   e.stopPropagation();
-  var element = e.target;
   var el = document.getElementById("cap1");
   el.label = "client: (" + e.clientX + "," + e.clientY + ")";
   parent.arguments[0].SimpleTest.is(e.clientX, 3, "mouse event clientX on sub frame 1");
@@ -36,7 +35,7 @@ function mouseMove(e) {
   frames[0].runTests();
 }
 
-window.addEventListener("mousemove", mouseMove, false);
+window.addEventListener("mousemove", mouseMove);
 
 </script>
 </window>
diff --git a/toolkit/content/tests/chrome/frame_subframe_origin_subframe2.xhtml b/toolkit/content/tests/chrome/frame_subframe_origin_subframe2.xhtml
index 9ea0f9ebfe65e..338877ff965a9 100644
--- a/toolkit/content/tests/chrome/frame_subframe_origin_subframe2.xhtml
+++ b/toolkit/content/tests/chrome/frame_subframe_origin_subframe2.xhtml
@@ -23,7 +23,6 @@ function runTests()
 
 function mouseMove(e) {
   e.stopPropagation();
-  var element = e.target;
   var el = document.getElementById("cap2");
   el.label = "client: (" + e.clientX + "," + e.clientY + ")";
   parent.parent.arguments[0].SimpleTest.is(e.clientX, 6, "mouse event clientX on sub frame 2");
@@ -32,7 +31,7 @@ function mouseMove(e) {
   parent.parent.close();
 }
 
-window.addEventListener("mousemove",mouseMove, false);
+window.addEventListener("mousemove", mouseMove);
 
 </script>
 </window>
diff --git a/toolkit/content/tests/chrome/test_arrowpanel.xhtml b/toolkit/content/tests/chrome/test_arrowpanel.xhtml
index 5e6ccd000eb2d..6da6648a73503 100644
--- a/toolkit/content/tests/chrome/test_arrowpanel.xhtml
+++ b/toolkit/content/tests/chrome/test_arrowpanel.xhtml
@@ -201,7 +201,7 @@ function* nextTest()
     }
 
     // Check that the transition occurs for an arrow panel with animate="true"
-    $("animatepanel").addEventListener("transitionend", transitionEnded, false);
+    $("animatepanel").addEventListener("transitionend", transitionEnded);
     $("animatepanel").openPopup($("topleft"), "after_start", 0, 0, false, false, null, "start");
     is($("animatepanel").state, "showing", "state is showing");
     yield;
diff --git a/toolkit/content/tests/chrome/test_autocomplete2.xhtml b/toolkit/content/tests/chrome/test_autocomplete2.xhtml
index e9a58c143b164..4a051357eb070 100644
--- a/toolkit/content/tests/chrome/test_autocomplete2.xhtml
+++ b/toolkit/content/tests/chrome/test_autocomplete2.xhtml
@@ -41,38 +41,31 @@ nsAutoCompleteSimpleResult.prototype = {
  defaultIndex: -1,
  errorDescription: null,
  matchCount: 0,
- getValueAt: function() { return this._param; },
- getCommentAt: function() { return null; },
- getStyleAt: function() { return null; },
- getImageAt: function() { return null; },
- getFinalCompleteValueAt: function() { return this.getValueAt(); },
- getLabelAt: function() { return null; },
- removeValueAt: function() {}
+ getValueAt() { return this._param; },
+ getCommentAt() { return null; },
+ getStyleAt() { return null; },
+ getImageAtn() { return null; },
+ getFinalCompleteValueAt() { return this.getValueAt(); },
+ getLabelAt() { return null; },
+ removeValueAt() {}
 };
 
 // A basic autocomplete implementation that either returns one result or none
 var autoCompleteSimpleID = Components.ID("0a2afbdb-f30e-47d1-9cb1-0cd160240aca");
 var autoCompleteSimpleName = "@mozilla.org/autocomplete/search;1?name=simple"
 var autoCompleteSimple = {
-  QueryInterface: function(iid) {
-    if (iid.equals(Ci.nsISupports) ||
-        iid.equals(Ci.nsIFactory) ||
-        iid.equals(Ci.nsIAutoCompleteSearch))
-      return this;
+  QueryInterface: ChromeUtils.generateQI(["nsIFactory", "nsIAutoCompleteSearch"]),
 
-    throw Components.Exception("", Cr.NS_ERROR_NO_INTERFACE);
-  },
-
-  createInstance: function(outer, iid) {
+  createInstance(outer, iid) {
     return this.QueryInterface(iid);
   },
 
-  startSearch: function(aString, aParam, aResult, aListener) {
+  startSearch(aString, aParam, aResult, aListener) {
     var result = new nsAutoCompleteSimpleResult(aString);
     aListener.onSearchResult(this, result);
   },
 
-  stopSearch: function() {}
+  stopSearch() {}
 };
 
 var componentManager = Components.manager
diff --git a/toolkit/content/tests/chrome/test_autocomplete3.xhtml b/toolkit/content/tests/chrome/test_autocomplete3.xhtml
index c2d9566563576..04a5117b6adb8 100644
--- a/toolkit/content/tests/chrome/test_autocomplete3.xhtml
+++ b/toolkit/content/tests/chrome/test_autocomplete3.xhtml
@@ -41,38 +41,31 @@ nsAutoCompleteSimpleResult.prototype = {
  defaultIndex: 0,
  errorDescription: null,
  matchCount: 0,
- getValueAt: function() { return this._param; },
- getCommentAt: function() { return null; },
- getStyleAt: function() { return null; },
- getImageAt: function() { return null; },
- getFinalCompleteValueAt: function() { return this.getValueAt(); },
- getLabelAt: function() { return null; },
- removeValueAt: function() {}
+ getValueAt() { return this._param; },
+ getCommentAt() { return null; },
+ getStyleAt() { return null; },
+ getImageAt() { return null; },
+ getFinalCompleteValueAt() { return this.getValueAt(); },
+ getLabelAt() { return null; },
+ removeValueAt() {}
 };
 
 // A basic autocomplete implementation that either returns one result or none
 var autoCompleteSimpleID = Components.ID("0a2afbdb-f30e-47d1-9cb1-0cd160240aca");
 var autoCompleteSimpleName = "@mozilla.org/autocomplete/search;1?name=simple"
 var autoCompleteSimple = {
-  QueryInterface: function(iid) {
-    if (iid.equals(Ci.nsISupports) ||
-        iid.equals(Ci.nsIFactory) ||
-        iid.equals(Ci.nsIAutoCompleteSearch))
-      return this;
+  QueryInterface: ChromeUtils.generateQI(["nsIFactory", "nsIAutoCompleteSearch"]),
 
-    throw Components.Exception("", Cr.NS_ERROR_NO_INTERFACE);
-  },
-
-  createInstance: function(outer, iid) {
+  createInstance(outer, iid) {
     return this.QueryInterface(iid);
   },
 
-  startSearch: function(aString, aParam, aResult, aListener) {
+  startSearch(aString, aParam, aResult, aListener) {
     var result = new nsAutoCompleteSimpleResult(aString);
     aListener.onSearchResult(this, result);
   },
 
-  stopSearch: function() {}
+  stopSearch() {}
 };
 
 var componentManager = Components.manager
@@ -142,7 +135,6 @@ function checkNext() {
 
 function checkResult() {
   var autocomplete = $("autocomplete");
-  var style = window.getComputedStyle(autocomplete);
 
   is(autocomplete.value, tests[currentTest].result,
      "Test " + currentTest + ": autocomplete.value should equal '" +
@@ -158,26 +150,38 @@ function checkResult() {
 
   ++currentTest;
 
-  if (currentTest < tests.length)
+  if (currentTest < tests.length) {
     setTimeout(checkNext, 0);
-  else {
+  } else {
     // TODO (bug 494809): Autocomplete-in-the-middle should take in count RTL
     // and complete on KEY_ArrowRight or KEY_ArrowLeft based on that.  It should also revert
     // what user has typed to far if he moves in the opposite direction.
     if (!autocomplete.value.includes(">>")) {
       // Test result if user accepts autocomplete suggestion.
       synthesizeKey("KEY_ArrowRight");
-      is(autocomplete.value, "Result",
-         "Test complete: autocomplete.value should equal 'Result'");
-      is(autocomplete.selectionStart, 6,
-         "Test complete: autocomplete selection should start at 6");
-      is(autocomplete.selectionEnd, 6,
-         "Test complete: autocomplete selection should end at 6");
+      is(
+        autocomplete.value,
+        "Result",
+        "Test complete: autocomplete.value should equal 'Result'"
+      );
+      is(
+        autocomplete.selectionStart,
+        6,
+        "Test complete: autocomplete selection should start at 6"
+      );
+      is(
+        autocomplete.selectionEnd,
+        6,
+        "Test complete: autocomplete selection should end at 6"
+      );
     }
 
-    setTimeout(function() {
+    setTimeout(function () {
       // Unregister the factory so that we don't get in the way of other tests
-      componentManager.unregisterFactory(autoCompleteSimpleID, autoCompleteSimple);
+      componentManager.unregisterFactory(
+        autoCompleteSimpleID,
+        autoCompleteSimple
+      );
       SimpleTest.finish();
     }, 0);
   }
diff --git a/toolkit/content/tests/chrome/test_autocomplete4.xhtml b/toolkit/content/tests/chrome/test_autocomplete4.xhtml
index 08c66ea03cb7d..9abf66ba19494 100644
--- a/toolkit/content/tests/chrome/test_autocomplete4.xhtml
+++ b/toolkit/content/tests/chrome/test_autocomplete4.xhtml
@@ -44,38 +44,31 @@ nsAutoCompleteSimpleResult.prototype = {
  defaultIndex: 0,
  errorDescription: null,
  matchCount: 0,
- getValueAt: function() { return this._param; },
- getCommentAt: function() { return null; },
- getStyleAt: function() { return null; },
- getImageAt: function() { return null; },
- getFinalCompleteValueAt: function() { return this.getValueAt(); },
- getLabelAt: function() { return null; },
- removeValueAt: function() {}
+ getValueAt() { return this._param; },
+ getCommentAt() { return null; },
+ getStyleAt() { return null; },
+ getImageAt() { return null; },
+ getFinalCompleteValueAt() { return this.getValueAt(); },
+ getLabelAt() { return null; },
+ removeValueAt() {}
 };
 
 // A basic autocomplete implementation that either returns one result or none
 var autoCompleteSimpleID = Components.ID("0a2afbdb-f30e-47d1-9cb1-0cd160240aca");
 var autoCompleteSimpleName = "@mozilla.org/autocomplete/search;1?name=simple"
 var autoCompleteSimple = {
-  QueryInterface: function(iid) {
-    if (iid.equals(Ci.nsISupports) ||
-        iid.equals(Ci.nsIFactory) ||
-        iid.equals(Ci.nsIAutoCompleteSearch))
-      return this;
+  QueryInterface: ChromeUtils.generateQI(["nsIFactory", "nsIAutoCompleteSearch"]),
 
-    throw Components.Exception("", Cr.NS_ERROR_NO_INTERFACE);
-  },
-
-  createInstance: function(outer, iid) {
+  createInstance(outer, iid) {
     return this.QueryInterface(iid);
   },
 
-  startSearch: function(aString, aParam, aResult, aListener) {
+  startSearch(aString, aParam, aResult, aListener) {
     var result = new nsAutoCompleteSimpleResult(aString);
     aListener.onSearchResult(this, result);
   },
 
-  stopSearch: function() {}
+  stopSearch() {}
 };
 
 var componentManager = Components.manager
@@ -221,7 +214,7 @@ function runCurrentTest() {
 
 function searchComplete() {
   var autocomplete = $("autocomplete");
-  autocomplete.setAttribute("forcecomplete", currentTest.forceComplete ? true : false);
+  autocomplete.setAttribute("forcecomplete", currentTest.forceComplete);
 
   if (currentTest.completeFromMiddle) {
     if (!currentTest.forceComplete) {
diff --git a/toolkit/content/tests/chrome/test_autocomplete5.xhtml b/toolkit/content/tests/chrome/test_autocomplete5.xhtml
index 94ece8d45d704..72cb081f6664a 100644
--- a/toolkit/content/tests/chrome/test_autocomplete5.xhtml
+++ b/toolkit/content/tests/chrome/test_autocomplete5.xhtml
@@ -37,38 +37,31 @@ nsAutoCompleteSimpleResult.prototype = {
  defaultIndex: -1,
  errorDescription: null,
  matchCount: 0,
- getValueAt: function() { return this._param; },
- getCommentAt: function() { return null; },
- getStyleAt: function() { return null; },
- getImageAt: function() { return null; },
- getFinalCompleteValueAt: function() { return this.getValueAt(); },
- getLabelAt: function() { return null; },
- removeValueAt: function() {}
+ getValueAt() { return this._param; },
+ getCommentAt() { return null; },
+ getStyleAt() { return null; },
+ getImageAt() { return null; },
+ getFinalCompleteValueAt() { return this.getValueAt(); },
+ getLabelAt() { return null; },
+ removeValueAt() {}
 };
 
 // A basic autocomplete implementation that either returns one result or none
 var autoCompleteSimpleID = Components.ID("0a2afbdb-f30e-47d1-9cb1-0cd160240aca");
 var autoCompleteSimpleName = "@mozilla.org/autocomplete/search;1?name=simple"
 var autoCompleteSimple = {
-  QueryInterface: function(iid) {
-    if (iid.equals(Ci.nsISupports) ||
-        iid.equals(Ci.nsIFactory) ||
-        iid.equals(Ci.nsIAutoCompleteSearch))
-      return this;
+  QueryInterface: ChromeUtils.generateQI(["nsIFactory", "nsIAutoCompleteSearch"]),
 
-    throw Components.Exception("", Cr.NS_ERROR_NO_INTERFACE);
-  },
-
-  createInstance: function(outer, iid) {
+  createInstance(outer, iid) {
     return this.QueryInterface(iid);
   },
 
-  startSearch: function(aString, aParam, aResult, aListener) {
+  startSearch(aString, aParam, aResult, aListener) {
     var result = new nsAutoCompleteSimpleResult(aString);
     aListener.onSearchResult(this, result);
   },
 
-  stopSearch: function() {}
+  stopSearch() {}
 };
 
 
@@ -129,7 +122,7 @@ function checkSearchCompleted() {
     hasSearchBegun = false;
     synthesizeKey("KEY_Escape");
   } else {
-    throw "checkSearchCompleted should only be called twice.";
+    throw new Error("checkSearchCompleted should only be called twice.");
   }
 }
 
diff --git a/toolkit/content/tests/chrome/test_autocomplete_emphasis.xhtml b/toolkit/content/tests/chrome/test_autocomplete_emphasis.xhtml
index f8c73b663753d..5155dee6874f7 100644
--- a/toolkit/content/tests/chrome/test_autocomplete_emphasis.xhtml
+++ b/toolkit/content/tests/chrome/test_autocomplete_emphasis.xhtml
@@ -42,38 +42,31 @@ nsAutoCompleteSimpleResult.prototype = {
  defaultIndex: -1,
  errorDescription: null,
  matchCount: 0,
- getValueAt: function() { return resultText; },
- getCommentAt: function() { return this.getValueAt(); },
- getStyleAt: function() { return null; },
- getImageAt: function() { return null; },
- getFinalCompleteValueAt: function() { return this.getValueAt(); },
- getLabelAt: function() { return this.getValueAt(); },
- removeValueAt: function() {}
+ getValueAt() { return resultText; },
+ getCommentAt() { return this.getValueAt(); },
+ getStyleAt() { return null; },
+ getImageAt() { return null; },
+ getFinalCompleteValueAt() { return this.getValueAt(); },
+ getLabelAt() { return this.getValueAt(); },
+ removeValueAt() {}
 };
 
 // A basic autocomplete implementation that returns the string contained in 'resultText'.
 var autoCompleteSimpleID = Components.ID("0a2afbdb-f30e-47d1-9cb1-0cd160240aca");
 var autoCompleteSimpleName = "@mozilla.org/autocomplete/search;1?name=simple"
 var autoCompleteSimple = {
-  QueryInterface: function(iid) {
-    if (iid.equals(Ci.nsISupports) ||
-        iid.equals(Ci.nsIFactory) ||
-        iid.equals(Ci.nsIAutoCompleteSearch))
-      return this;
+  QueryInterface: ChromeUtils.generateQI(["nsIFactory", "nsIAutoCompleteSearch"]),
 
-    throw Components.Exception("", Cr.NS_ERROR_NO_INTERFACE);
-  },
-
-  createInstance: function(outer, iid) {
+  createInstance(outer, iid) {
     return this.QueryInterface(iid);
   },
 
-  startSearch: function(aString, aParam, aResult, aListener) {
+  startSearch(aString, aParam, aResult, aListener) {
     var result = new nsAutoCompleteSimpleResult(aString);
     aListener.onSearchResult(this, result);
   },
 
-  stopSearch: function() {}
+  stopSearch() {}
 };
 
 var componentManager = Components.manager
diff --git a/toolkit/content/tests/chrome/test_autocomplete_placehold_last_complete.xhtml b/toolkit/content/tests/chrome/test_autocomplete_placehold_last_complete.xhtml
index f2e8fed03d310..15ed2dfda9053 100644
--- a/toolkit/content/tests/chrome/test_autocomplete_placehold_last_complete.xhtml
+++ b/toolkit/content/tests/chrome/test_autocomplete_placehold_last_complete.xhtml
@@ -43,12 +43,12 @@ autoCompleteSimpleResult.prototype = {
   defaultIndex: 0,
   errorDescription: null,
   matchCount: 0,
-  getValueAt: function() { return this._param; },
-  getCommentAt: function() { return null; },
-  getStyleAt: function() { return null; },
-  getImageAt: function() { return null; },
-  getLabelAt: function() { return null; },
-  removeValueAt: function() {}
+  getValueAt() { return this._param; },
+  getCommentAt() { return null; },
+  getStyleAt() { return null; },
+  getImageAt() { return null; },
+  getLabelAt() { return null; },
+  removeValueAt() {}
 };
 
 var searchCounter = 0;
@@ -64,23 +64,23 @@ let autoCompleteSimple = {
     "nsIFactory",
     "nsIAutoCompleteSearch"
   ]),
-  createInstance: function (outer, iid) {
+  createInstance(outer, iid) {
     return this.QueryInterface(iid);
   },
 
-  registerFactory: function () {
+  registerFactory() {
     let registrar =
       Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
     registrar.registerFactory(this.classID, "Test Simple Autocomplete",
                               this.contractID, this);
   },
-  unregisterFactory: function () {
+  unregisterFactory() {
     let registrar =
       Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
     registrar.unregisterFactory(this.classID, this);
   },
 
-  startSearch: function (aString, aParam, aResult, aListener) {
+  startSearch(aString, aParam, aResult, aListener) {
     let result = new autoCompleteSimpleResult(aString);
 
     if (this.searchAsync) {
@@ -99,7 +99,7 @@ let autoCompleteSimple = {
       aListener.onSearchResult(this, result);
     }
   },
-  stopSearch: function () {
+  stopSearch() {
     clearTimeout(this.pendingSearch);
   }
 };
diff --git a/toolkit/content/tests/chrome/test_bug1048178.xhtml b/toolkit/content/tests/chrome/test_bug1048178.xhtml
index 6199bd27a67f4..302835e3b9f16 100644
--- a/toolkit/content/tests/chrome/test_bug1048178.xhtml
+++ b/toolkit/content/tests/chrome/test_bug1048178.xhtml
@@ -30,13 +30,13 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=1048178
 /** Test for Bug 1048178 **/
 var scrollbarTester = {
   scrollbar: null,
-  startTest: function() {
+  startTest() {
     this.scrollbar = $("scroller");
     this.setScrollToClick(false);
     this.testThumbDragging();
     SimpleTest.finish();
   },
-  testThumbDragging: function() {
+  testThumbDragging() {
     var x = 400; // on the right half of the scroolbar
     var y = 5;
 
@@ -55,22 +55,21 @@ var scrollbarTester = {
     ok(newPos2 < newPos,
        "Scrollbar thumb should follow the mouse when dragged.");
   },
-  setScrollToClick: function(value) {
-    var prefService = Cc["@mozilla.org/preferences-service;1"]
-                        .getService(Ci.nsIPrefService);
+  setScrollToClick(value) {
+    var prefService = SpecialPowers.Services.prefs.nsIPrefService;
     var uiBranch = prefService.getBranch("ui.");
     uiBranch.setIntPref("scrollToClick", value ? 1 : 0);
   },
-  getPos: function() {
+  getPos() {
     return this.scrollbar.getAttribute("curpos");
   },
-  mousedown: function(x, y, button) {
+  mousedown(x, y, button) {
     synthesizeMouse(this.scrollbar, x, y, { type: "mousedown", 'button': button });
   },
-  mousemove: function(x, y, button) {
+  mousemove(x, y, button) {
     synthesizeMouse(this.scrollbar, x, y, { type: "mousemove", 'button': button });
   },
-  mouseup: function(x, y, button) {
+  mouseup(x, y, button) {
     synthesizeMouse(this.scrollbar, x, y, { type: "mouseup", 'button': button });
   }
 }
diff --git a/toolkit/content/tests/chrome/test_bug437844.xhtml b/toolkit/content/tests/chrome/test_bug437844.xhtml
index 5d59757b63e9d..5bc06e098774b 100644
--- a/toolkit/content/tests/chrome/test_bug437844.xhtml
+++ b/toolkit/content/tests/chrome/test_bug437844.xhtml
@@ -42,8 +42,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=348233
       /** Test for Bug 437844 and Bug 348233 **/
       SimpleTest.waitForExplicitFinish();
 
-      let prefs = Cc["@mozilla.org/preferences-service;1"]
-                    .getService(Ci.nsIPrefBranch);
+      let prefs = SpecialPowers.Services.prefs.nsIPrefBranch;
       prefs.setIntPref("intl.uidirection", 1);
 
       let rootDir = getRootDirectory(window.location.href);
@@ -66,27 +65,22 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=348233
       let frame = document.createXULElement("iframe");
       frame.setAttribute("src", "about:plugins");
       frame.addEventListener("load", function () {
-          frame.removeEventListener("load", arguments.callee, false);
           is(frame.contentDocument.dir, "rtl", "about:plugins should be RTL in RTL locales");
 
-          let gDirSvc    = Cc["@mozilla.org/file/directory_service;1"].
-                                      getService(Ci.nsIDirectoryService).
-                                      QueryInterface(Ci.nsIProperties);
-          let tmpd = gDirSvc.get("ProfD", Ci.nsIFile);
+          // eslint-disable-next-line no-unused-vars
+          let tmpd = SpecialPowers.Services.dirsvc.get("ProfD", Ci.nsIFile);
 
           frame = document.createXULElement("iframe");
           frame.setAttribute("src", "file://" + tmpd.path); // a file:// URI, bug 348233
           frame.addEventListener("load", function () {
-              frame.removeEventListener("load", arguments.callee, false);
-
               is(frame.contentDocument.body.dir, "rtl", "file:// listings should be RTL in RTL locales");
 
               cleanupFunc();
               prefs.clearUserPref("intl.uidirection");
               SimpleTest.finish();
-            }, false);
+            });
           document.documentElement.appendChild(frame);
-        }, false);
+        }, { once: true });
       document.documentElement.appendChild(frame);
 
     ]]>
diff --git a/toolkit/content/tests/chrome/test_bug624329.xhtml b/toolkit/content/tests/chrome/test_bug624329.xhtml
index 59b57a1607f1d..7000cbc66a56f 100644
--- a/toolkit/content/tests/chrome/test_bug624329.xhtml
+++ b/toolkit/content/tests/chrome/test_bug624329.xhtml
@@ -40,9 +40,8 @@ function openTestWindow() {
 
 function listenOnce(event, callback) {
     win.addEventListener(event, function listener() {
-        win.removeEventListener(event, listener, false);
         callback();
-    }, false);
+    }, { once: true});
 }
 
 function childFocused() {
diff --git a/toolkit/content/tests/chrome/test_bug792324.xhtml b/toolkit/content/tests/chrome/test_bug792324.xhtml
index febc93288e58c..ddedf5907b406 100644
--- a/toolkit/content/tests/chrome/test_bug792324.xhtml
+++ b/toolkit/content/tests/chrome/test_bug792324.xhtml
@@ -47,7 +47,6 @@ function clicked(event) {
 function checkAccessKeyOnPanel(panelid, buttonid, cb) {
   let panel = document.getElementById(panelid);
   panel.addEventListener("popupshown", function onpopupshown() {
-    panel.removeEventListener("popupshown", onpopupshown);
     panel.firstChild.focus();
     after_click = function(event) {
       is(event.target.id, buttonid, "Accesskey was directed to the button '" + buttonid + "'");
diff --git a/toolkit/content/tests/chrome/test_contextmenu_list.xhtml b/toolkit/content/tests/chrome/test_contextmenu_list.xhtml
index 798c94e343861..8fb5f112d0444 100644
--- a/toolkit/content/tests/chrome/test_contextmenu_list.xhtml
+++ b/toolkit/content/tests/chrome/test_contextmenu_list.xhtml
@@ -163,12 +163,12 @@ function nextTest()
 
 function isRoundedX(a, b, msg)
 {
-  is(Math.round(a + mozInnerScreenX), Math.round(b + mozInnerScreenX), msg);
+  is(Math.round(a + window.mozInnerScreenX), Math.round(b + window.mozInnerScreenX), msg);
 }
 
 function isRoundedY(a, b, msg)
 {
-  is(Math.round(a + mozInnerScreenY), Math.round(b + mozInnerScreenY), msg);
+  is(Math.round(a + window.mozInnerScreenY), Math.round(b + window.mozInnerScreenY), msg);
 }
 
 function checkContextMenu(event)
@@ -189,6 +189,7 @@ function checkContextMenu(event)
   // context menu from mouse click
   switch (gTestId) {
     case -1:
+      // eslint-disable-next-line no-nested-ternary
       var expected = gSelectionStep == 2 ? 1 : (platformIsMac() ? 3 : 0);
       is($(gTestElement).selectedIndex, expected, "index after click " + gSelectionStep);
       break;
@@ -251,14 +252,14 @@ function checkPopup()
   }
   else if (gTestId == 1) {
     // activating a context menu with the mouse from position (7, 4).
-    var elementrect = $(gTestElement).getBoundingClientRect();
+    let elementrect = $(gTestElement).getBoundingClientRect();
     isRoundedX(menurect.left, elementrect.left + 7 + contextMenuOffsetX,
        gTestElement + " mouse left");
     isRoundedY(menurect.top, elementrect.top + 4 + contextMenuOffsetY,
        gTestElement + " mouse top");
   }
   else {
-    var elementrect = $(gTestElement).getBoundingClientRect();
+    let elementrect = $(gTestElement).getBoundingClientRect();
     isRoundedX(menurect.left, elementrect.left + contextMenuOffsetX,
        gTestElement + " no selection keyboard left");
     isRoundedY(menurect.top, elementrect.bottom + contextMenuOffsetY,
diff --git a/toolkit/content/tests/chrome/test_cursorsnap.xhtml b/toolkit/content/tests/chrome/test_cursorsnap.xhtml
index 0e9e3758a6121..f83938fbb7114 100644
--- a/toolkit/content/tests/chrome/test_cursorsnap.xhtml
+++ b/toolkit/content/tests/chrome/test_cursorsnap.xhtml
@@ -101,14 +101,12 @@ function runCurrentTest()
     default:
       SetPrefs(false);
       SimpleTest.finish();
-      return;
   }
 }
 
 function SetPrefs(aSet)
 {
-  var prefSvc = Cc["@mozilla.org/preferences-service;1"].
-                           getService(Ci.nsIPrefBranch);
+  var prefSvc = SpecialPowers.Services.prefs.nsIPrefBranch;
   const kPrefName = "ui.cursor_snapping.always_enabled";
   if (aSet) {
     prefSvc.setBoolPref(kPrefName, true);
diff --git a/toolkit/content/tests/chrome/test_menu.xhtml b/toolkit/content/tests/chrome/test_menu.xhtml
index 6ec9501a074f8..8ef5c4ca15abd 100644
--- a/toolkit/content/tests/chrome/test_menu.xhtml
+++ b/toolkit/content/tests/chrome/test_menu.xhtml
@@ -52,7 +52,7 @@
         "nsIDOMXULContainerElement::parentContainer failed.");
 
     // nsIDOMXULContainerElement::appendItem();
-    var item = menu.appendItem("item3");
+    item = menu.appendItem("item3");
     is(menu.getIndexOfItem(item), 2,
        "nsIDOMXULContainerElement::appendItem() failed.");
 
diff --git a/toolkit/content/tests/chrome/test_menuitem_blink.xhtml b/toolkit/content/tests/chrome/test_menuitem_blink.xhtml
index ccb8f8204c649..3340f0b7b604f 100644
--- a/toolkit/content/tests/chrome/test_menuitem_blink.xhtml
+++ b/toolkit/content/tests/chrome/test_menuitem_blink.xhtml
@@ -45,10 +45,8 @@ function test_crash(when, andThen) {
   var attrChanges = { "REMOVAL": 0, "ADDITION": 0 };
   var storedEvent = null;
   menupopup.addEventListener("popupshown", function () {
-    menupopup.removeEventListener("popupshown", arguments.callee, false);
     menuitem.addEventListener("mouseup", function (e) {
-      menuitem.removeEventListener("mouseup", arguments.callee, true);
-      menuitem.addEventListener("DOMAttrModified", function (e) {
+      menuitem.addEventListener("DOMAttrModified", function onDOMAttrModified(e) {
         if (e.target != e.currentTarget) {
           return;
         }
@@ -63,16 +61,15 @@ function test_crash(when, andThen) {
             menuitem.getBoundingClientRect();
             ok(true, "Didn't crash on _moz-menuactive " + when.toLowerCase() + " during blinking")
             menuitem.hidden = false;
-            menuitem.removeEventListener("DOMAttrModified", arguments.callee, false);
+            menuitem.removeEventListener("DOMAttrModified", onDOMAttrModified);
             SimpleTest.executeSoon(function () {
               menupopup.hidePopup();
             });
           }
         }
-      }, false);
-    }, true);
+      });
+    }, {once: true});
     menupopup.addEventListener("popuphidden", function() {
-      menupopup.removeEventListener("popuphidden", arguments.callee, false);
       if (!when) {
         // Test whether we've blinked at all.
         var shouldBlink = navigator.platform.match(/Mac/);
@@ -83,14 +80,14 @@ function test_crash(when, andThen) {
         is(attrChanges[storedEvent.ADDITION], expectedNumAddition, "blinking set attributes correctly");
       }
       SimpleTest.executeSoon(andThen);
-    }, false);
+    }, {once: true});
     synthesizeMouse(menuitem, 10, 5, { type : "mousemove" });
     synthesizeMouse(menuitem, 10, 5, { type : "mousemove" });
     synthesizeMouse(menuitem, 10, 5, { type : "mousedown" });
     SimpleTest.executeSoon(function () {
       synthesizeMouse(menuitem, 10, 5, { type : "mouseup" });
     });
-  }, false);
+  }, {once: true});
   document.getElementById("menulist").open = true;
 }
 
diff --git a/toolkit/content/tests/chrome/test_menulist.xhtml b/toolkit/content/tests/chrome/test_menulist.xhtml
index df9e8253065f8..4181d7f44f12e 100644
--- a/toolkit/content/tests/chrome/test_menulist.xhtml
+++ b/toolkit/content/tests/chrome/test_menulist.xhtml
@@ -153,7 +153,7 @@ function test_nsIDOMXULMenuListElement(element)
 function test_nsIDOMXULMenuListElement_properties(element, thirditem, properties)
 {
   let {attr, value} = properties.shift();
-  let last = (properties.length == 0);
+  let last = !properties.length;
 
   let mutObserver = new MutationObserver(() => {
     is(element.getAttribute(attr), value, `${attr} modified`);