[chromedriver] Allow commands to be async. Run all commands on comman…

…d thread.

This is in preparation for switching from mongoose to net::HttpServer.
BUG=none
[email protected]

Review URL: https://codereview.chromium.org/19977002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@213200 0039d316-1c4b-4281-b951-d872f2087c98

README.txt

@@ -4,10 +4,12 @@ contribute.
 ChromeDriver is an implementation of the WebDriver standard,
 which allows users to automate testing of their website across browsers.
 
+See the user site at http://code.google.com/p/chromedriver.
+
 =====Getting started=====
 Build ChromeDriver by building the 'chromedriver2_server' target. This will
-create an executable binary in the build folder named 'chromedriver2_server.exe'
-on Windows or 'chromedriver2_server' on Mac and Linux.
+create an executable binary in the build folder named
+'chromedriver2_server[.exe]'.
 
 Once built, ChromeDriver can be used interactively with python.
 
@@ -31,26 +33,30 @@ more detailed instructions see the wiki:
 
 =====Architecture=====
 ChromeDriver is shipped separately from Chrome. It controls Chrome out of
-process through DevTools (WebKit Inspector). ChromeDriver is a standalone server
-executable which communicates via the WebDriver JSON wire protocol. This can be
-used with the open source WebDriver client libraries.
-
-When a new session is created, a new thread is started that is dedicated to the
-session. All commands for the session runs on this thread. This thread is
-stopped when the session is deleted. Besides, there is an IO thread and it is
-used to keep reading incoming data from Chrome in the background.
+process through DevTools. ChromeDriver is a standalone server which
+communicates with the WebDriver client via the WebDriver wire protocol, which
+is essentially synchronous JSON commands over HTTP. WebDriver clients are
+available in many languages, and many are available from the open source
+selenium/webdriver project: http://code.google.com/p/selenium.
+
+ChromeDriver has several threads. The webserver code, third_party/mongoose,
+spawns a thread for the server socket and a certain amount of request handling
+threads. When a request is received, the command is processed on the message
+loop of the main thread, also called the command thread. Commands may be handled
+asynchronously on the command thread, but the request handler threads
+will block waiting for the response. One of the commands allows the user to
+create a session, which includes spawning a dedicated session thread. Session
+commands will be dispatched to the session thread and handled synchronously
+there. Lastly, there is an IO/net thread on which the net/ code operates.
+This is used to keep reading incoming data from Chrome in the background.
 
 =====Code structure=====
-Code under the 'chrome' subdirectory is intended to be unaware of WebDriver and
-serve as a basic C++ interface for controlling Chrome remotely via DevTools.
-As such, it should not have any WebDriver-related dependencies.
-
 1) chrome/test/chromedriver
 Implements chromedriver commands.
 
 2) chrome/test/chromedriver/chrome
-Code to deal with chrome specific stuff, like starting Chrome on different OS
-platforms, controlling Chrome via DevTools, handling events from DevTools, etc.
+A basic interface for controlling Chrome via DevTools. Should not have
+knowledge about WebDriver, and thus not depend on chrome/test/chromedriver.
 
 3) chrome/test/chromedriver/js
 Javascript helper scripts.
@@ -71,6 +77,9 @@ An extension used for automating the desktop browser.
 8) chrome/test/chromedriver/third_party
 Third party libraries used by chromedriver.
 
+9) third_party/mongoose
+The webserver for chromedriver.
+
 =====Testing=====
 There are 4 test suites for verifying ChromeDriver's correctness:
 

alert_commands.cc

@@ -4,6 +4,7 @@
 
 #include "chrome/test/chromedriver/alert_commands.h"
 
+#include "base/callback.h"
 #include "base/values.h"
 #include "chrome/test/chromedriver/chrome/chrome.h"
 #include "chrome/test/chromedriver/chrome/devtools_client.h"

chrome/adb_impl.cc

@@ -9,7 +9,7 @@
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_loop/message_loop.h"
-#include "base/message_loop/message_loop_proxy.h"
+#include "base/single_thread_task_runner.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_tokenizer.h"
@@ -71,10 +71,10 @@ void ExecuteCommandOnIOThread(
 }  // namespace
 
 AdbImpl::AdbImpl(
-    const scoped_refptr<base::MessageLoopProxy>& io_message_loop_proxy,
+    const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner,
     Log* log)
-    : io_message_loop_proxy_(io_message_loop_proxy), log_(log) {
-  CHECK(io_message_loop_proxy_.get());
+    : io_task_runner_(io_task_runner), log_(log) {
+  CHECK(io_task_runner_.get());
 }
 
 AdbImpl::~AdbImpl() {}
@@ -185,7 +185,7 @@ Status AdbImpl::ExecuteCommand(
     const std::string& command, std::string* response) {
   scoped_refptr<ResponseBuffer> response_buffer = new ResponseBuffer;
   log_->AddEntry(Log::kDebug, "Sending adb command: " + command);
-  io_message_loop_proxy_->PostTask(
+  io_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&ExecuteCommandOnIOThread, command, response_buffer));
   Status status = response_buffer->GetResponse(

chrome/adb_impl.h

@@ -13,7 +13,7 @@
 #include "chrome/test/chromedriver/chrome/adb.h"
 
 namespace base {
-class MessageLoopProxy;
+class SingleThreadTaskRunner;
 }
 
 class Log;
@@ -22,7 +22,7 @@ class Status;
 class AdbImpl : public Adb {
  public:
   explicit AdbImpl(
-      const scoped_refptr<base::MessageLoopProxy>& io_message_loop_proxy,
+      const scoped_refptr<base::SingleThreadTaskRunner>& io_message_loop_proxy,
       Log* log);
   virtual ~AdbImpl();
 
@@ -53,7 +53,7 @@ class AdbImpl : public Adb {
                                  const std::string& shell_command,
                                  std::string* response);
 
-  scoped_refptr<base::MessageLoopProxy> io_message_loop_proxy_;
+  scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
 
   Log* log_;
 };

command.h

@@ -17,10 +17,14 @@ class Value;
 
 class Status;
 
-typedef base::Callback<Status(
+typedef base::Callback<void(
+    const Status&,
+    scoped_ptr<base::Value>,
+    const std::string&)> CommandCallback;
+
+typedef base::Callback<void(
     const base::DictionaryValue&,
     const std::string&,
-    scoped_ptr<base::Value>*,
-    std::string*)> Command;
+    const CommandCallback&)> Command;
 
 #endif  // CHROME_TEST_CHROMEDRIVER_COMMAND_H_