Use SingleThreadTaskRunner instead of MessageLoopProxy in remoting/host.

remoting/host/chromoting_host_context.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef REMOTING_HOST_CHROMOTING_HOST_CONTEXT_H_
 #define REMOTING_HOST_CHROMOTING_HOST_CONTEXT_H_
 
 #include <string>
 
 #include "base/gtest_prod_util.h"
+#include "base/memory/ref_counted.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/thread.h"
 #include "remoting/jingle_glue/jingle_thread.h"
 
+namespace base {
+class SingleThreadTaskRunner;
+}  // namespace base
+
 namespace net {
 class URLRequestContextGetter;
 }  // namespace net
 
 namespace remoting {
 
 // A class that manages threads and running context for the chromoting host
 // process.  This class is virtual only for testing purposes (see below).
 class ChromotingHostContext {
  public:
   // Create a context.
-  ChromotingHostContext(base::MessageLoopProxy* ui_message_loop);
+  ChromotingHostContext(
+      scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner);
   virtual ~ChromotingHostContext();
 
   // TODO(ajwong): Move the Start method out of this class. Then
   // create a static factory for construction, and destruction.  We
   // should be able to remove the need for virtual functions below
   // with that design, while preserving the relative simplicity of
   // this API.
   virtual bool Start();
 
   virtual JingleThread* jingle_thread();
 
-  virtual MessageLoop* main_message_loop();
-  virtual MessageLoop* encode_message_loop();
-  virtual base::MessageLoopProxy* network_message_loop();
-  virtual MessageLoop* desktop_message_loop();
-  virtual base::MessageLoopProxy* ui_message_loop();
-  virtual base::MessageLoopProxy* io_message_loop();
-  virtual base::MessageLoopProxy* file_message_loop();
+  // Task runned for the thread that is used for UI. In the NPAPI

[Wez, 2012/06/19 18:30:21]

typo: runned -> runner
typo: UI -> the UI

[Sergey Ulanov, 2012/06/19 19:01:41]

Done.

+  // plugin this corresponds to the main plugin thread.
+  virtual base::SingleThreadTaskRunner* ui_task_runner();
+
+  // Task runner for the thread used by the ScreenRecorder to capture
+  // the screen.
+  virtual base::SingleThreadTaskRunner* capture_task_runner();
+
+  // Task runner for the thread used to encode video streams.
+  virtual base::SingleThreadTaskRunner* encode_task_runner();
+
+  // Network thread is the thread use for most networking IO. It runs
+  // libjingle's message loop, so libjingle code should be used only
+  // on this thread.

[Wez, 2012/06/19 18:30:21]

nit: Reword this to the same style as the others e.g:
"Task runner for the thread used for network IO. This thread runs a libjingle
message loop, and is the only thread on which libjingle code may be run."

[Sergey Ulanov, 2012/06/19 19:01:41]

Done.

+  virtual base::SingleThreadTaskRunner* network_task_runner();
+
+  // Task runner for the thread that is used by the EventExecutor.
+  //
+  // TODO(sergeyu): Do we need a separate thread for EventExecutor?
+  // Can we use some other thread instead?
+  virtual base::SingleThreadTaskRunner* desktop_task_runner();
+
+  // Task runner for the thread that is used for network IO. Note that
+  // most of network IO for remoting happens on a different thread,
+  // the one that corresponds to network_task_runner(). This is
+  // because libjingle code needs to work on a thread that runs
+  // libjingle's message loop.

[Wez, 2012/06/19 18:30:21]

This is confusing; what networking do we run on io_task_runner and why not run
it all on network_task_runner? If the issue is that we can't do some kinds of
network IO on network_task_runner because of the libjingle message loop then
that should be called out more clearly.

[Sergey Ulanov, 2012/06/19 19:01:41]

All HTTP requests, specifically for oauth and relay session allocation.
Because chromium sockets work only on threads with MessageLoopForIO.
Done

+  //
+  // TODO(sergeyu): Implement socket server for libjingle that works
+  // on a regular chromium thread and use it for network_task_runner()
+  // to avoid the need for io_task_runner().
+  virtual base::SingleThreadTaskRunner* io_task_runner();
+
+  // Task runner for the thread that is used for file IO.

[Wez, 2012/06/19 18:30:21]

nit: Why do we keep this separate from the IO thread above? Consider giving an
example of the file IO we perform?

[Sergey Ulanov, 2012/06/19 19:01:41]

changed "file IO" to "blocking file IO".
Done

+  virtual base::SingleThreadTaskRunner* file_task_runner();
+
   const scoped_refptr<net::URLRequestContextGetter>&
       url_request_context_getter();
 
  private:
   FRIEND_TEST_ALL_PREFIXES(ChromotingHostContextTest, StartAndStop);
 
   // A thread that hosts all network operations.
   JingleThread jingle_thread_;
 
-  // TODO(sergeyu): The "main" thread is used just by the
-  // capturer. Consider renaming it.
-  base::Thread main_thread_;
+  // A thread that hosts screen capture.
+  base::Thread capture_thread_;
 
   // A thread that hosts all encode operations.
   base::Thread encode_thread_;
 
-  // A thread that hosts desktop integration (capture, input injection, etc)
-  // This is NOT a Chrome-style UI thread.
+  // A thread that hosts input injection.
   base::Thread desktop_thread_;
 
   // Thread for non-blocking IO operations.
   base::Thread io_thread_;
 
   // Thread for blocking IO operations.
   base::Thread file_thread_;
 
-  scoped_refptr<base::MessageLoopProxy> ui_message_loop_;
+  scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner_;
 
   scoped_refptr<net::URLRequestContextGetter> url_request_context_getter_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromotingHostContext);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_HOST_CHROMOTING_HOST_CONTEXT_H_