Eliminate video capture thread in renderer

content/renderer/media/video_capture_impl.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.
 
 // VideoCaptureImpl represents a capture device in renderer process. It provides
 // interfaces for clients to Start/Stop capture. It also communicates to clients
 // when buffer is ready, state of capture device is changed.
 
 // VideoCaptureImpl is also a delegate of VideoCaptureMessageFilter which relays
 // operation of a capture device to the browser process and receives responses
 // from browser process.
-
-// The media::VideoCapture and VideoCaptureMessageFilter::Delegate are
-// asynchronous interfaces, which means callers can call those interfaces
-// from any threads without worrying about thread safety.
-// The |capture_message_loop_proxy_| is the working thread of VideoCaptureImpl.
-// All non-const members are accessed only on that working thread.
 //
-// Implementation note: tasks are posted bound to Unretained(this) to both the
-// I/O and Capture threads and this is safe (even though the I/O thread is
-// scoped to the renderer process and the capture_message_loop_proxy_ thread is
-// scoped to the VideoCaptureImplManager) because VideoCaptureImplManager only
-// triggers deletion of its VideoCaptureImpl's by calling DeInit which detours
-// through the capture & I/O threads, so as long as nobody posts tasks after the
-// DeInit() call is made, it is guaranteed none of these Unretained posted tasks
-// will dangle after the delete goes through.  The "as long as" is guaranteed by
-// clients of VideoCaptureImplManager not using devices after they've
-// RemoveDevice'd them.
+// The media::VideoCapture and VideoCaptureMessageFilter::Delegate interfaces
+// can be called on any thread. Other public methods of VideoCaptureImpl can
+// be called on any thread. Internally it runs on the IO thread. Client of this

[Ami GONE FROM CHROMIUM, 2014/01/08 22:41:10]

Do the first two sentences of this paragraph summarize to "All public methods
can be called on any threads."?

[Ami GONE FROM CHROMIUM, 2014/01/08 22:41:10]

I think you missed this comment:

On 2014/01/08 01:43:58, Ami Fischman wrote:

[Alpha Left Google, 2014/01/08 22:57:05]

Done.

+// class implements interface media::VideoCapture::EventHandler which is called

[Ami GONE FROM CHROMIUM, 2014/01/08 22:41:10]

I don't see it.

[Alpha Left Google, 2014/01/08 22:57:05]

Done.

+// only on the IO thread.
+//
+// Implementation note: tasks are posted bound to Unretained(this) to the I/O
+// thread and this is safe (even though the I/O thread is scoped to the renderer
+// process) because VideoCaptureImplManager only triggers deletion of its
+// VideoCaptureImpl's by calling DeInit which detours through the I/O thread, so
+// as long as nobody posts tasks after the DeInit() call is made, it is
+// guaranteed none of these Unretained posted tasks will dangle after the delete
+// goes through. The "as long as" is guaranteed by clients of
+// VideoCaptureImplManager not using devices after they've released
+// VideoCaptureHandle, which is a wrapper of this object.
 
 #ifndef CONTENT_RENDERER_MEDIA_VIDEO_CAPTURE_IMPL_H_
 #define CONTENT_RENDERER_MEDIA_VIDEO_CAPTURE_IMPL_H_
 
 #include <list>
 #include <map>
 
 #include "base/memory/weak_ptr.h"
 #include "content/common/content_export.h"
 #include "content/common/media/video_capture.h"
 #include "content/renderer/media/video_capture_message_filter.h"
 #include "media/video/capture/video_capture.h"
 #include "media/video/capture/video_capture_types.h"
 
 namespace base {
 class MessageLoopProxy;
 }
 
 namespace content {
 
 class CONTENT_EXPORT VideoCaptureImpl
     : public media::VideoCapture, public VideoCaptureMessageFilter::Delegate {
  public:
+  VideoCaptureImpl(media::VideoCaptureSessionId session_id,
+                   VideoCaptureMessageFilter* filter);
+  virtual ~VideoCaptureImpl();
+
+  // Start listening to IPC messages.
+  void Init();
+
+  // Stop listening to IPC messages. Call |done_cb| when done.
+  void DeInit(base::Closure done_cb);
+
+  // Stop/resume delivering video frames to clients, based on flag |suspend|.
+  void SuspendCapture(bool suspend);
+
   // media::VideoCapture interface.
   virtual void StartCapture(
       media::VideoCapture::EventHandler* handler,
       const media::VideoCaptureParams& params) OVERRIDE;
   virtual void StopCapture(media::VideoCapture::EventHandler* handler) OVERRIDE;
   virtual bool CaptureStarted() OVERRIDE;
   virtual int CaptureFrameRate() OVERRIDE;
 
-  // VideoCaptureMessageFilter::Delegate interface.
-  virtual void OnBufferCreated(base::SharedMemoryHandle handle,
-                               int length,
-                               int buffer_id) OVERRIDE;
-  virtual void OnBufferDestroyed(int buffer_id) OVERRIDE;
-  virtual void OnBufferReceived(
-      int buffer_id,
-      base::Time timestamp,
-      const media::VideoCaptureFormat& format) OVERRIDE;
-  virtual void OnStateChanged(VideoCaptureState state) OVERRIDE;
-  virtual void OnDelegateAdded(int32 device_id) OVERRIDE;
-
-  // Stop/resume delivering video frames to clients, based on flag |suspend|.
-  virtual void SuspendCapture(bool suspend);
+  media::VideoCaptureSessionId session_id() const { return session_id_; }
 
  private:
-  friend class VideoCaptureImplManager;
   friend class VideoCaptureImplTest;
   friend class MockVideoCaptureImpl;
 
   class ClientBuffer;
   typedef std::map<media::VideoCapture::EventHandler*,
                    media::VideoCaptureParams> ClientInfo;
 
-  VideoCaptureImpl(media::VideoCaptureSessionId session_id,
-                   base::MessageLoopProxy* capture_message_loop_proxy,
-                   VideoCaptureMessageFilter* filter);
-  virtual ~VideoCaptureImpl();
-
-  void DoStartCaptureOnCaptureThread(
+  void InitOnIOThread();
+  void DeInitOnIOThread(base::Closure done_cb);
+  void SuspendCaptureOnIOThread(bool suspend);
+  void StartCaptureOnIOThread(
       media::VideoCapture::EventHandler* handler,
       const media::VideoCaptureParams& params);
-  void DoStopCaptureOnCaptureThread(media::VideoCapture::EventHandler* handler);
-  void DoBufferCreatedOnCaptureThread(base::SharedMemoryHandle handle,
-                                      int length,
-                                      int buffer_id);
-  void DoBufferDestroyedOnCaptureThread(int buffer_id);
-  void DoBufferReceivedOnCaptureThread(
+  void StopCaptureOnIOThread(media::VideoCapture::EventHandler* handler);
+
+  // VideoCaptureMessageFilter::Delegate interface.
+  virtual void OnBufferCreated(base::SharedMemoryHandle handle,
+                               int length,
+                               int buffer_id) OVERRIDE;
+  virtual void OnBufferDestroyed(int buffer_id) OVERRIDE;
+  virtual void OnBufferReceived(
       int buffer_id,
       base::Time timestamp,
-      const media::VideoCaptureFormat& format);
-  void DoClientBufferFinishedOnCaptureThread(
+      const media::VideoCaptureFormat& format) OVERRIDE;
+  virtual void OnStateChanged(VideoCaptureState state) OVERRIDE;
+  virtual void OnDelegateAdded(int32 device_id) OVERRIDE;
+
+  // Sends an IPC message to browser process when all clients are done with the
+  // buffer.
+  void OnClientBufferFinished(
       int buffer_id,
       const scoped_refptr<ClientBuffer>& buffer);
-  void DoStateChangedOnCaptureThread(VideoCaptureState state);
-  void DoDelegateAddedOnCaptureThread(int32 device_id);
 
-  void DoSuspendCaptureOnCaptureThread(bool suspend);
-
-  void Init();
-  void DeInit(base::Closure task);
-  void DoDeInitOnCaptureThread(base::Closure task);
   void StopDevice();
   void RestartCapture();
   void StartCaptureInternal();
-  void AddDelegateOnIOThread();
-  void RemoveDelegateOnIOThread(base::Closure task);
   virtual void Send(IPC::Message* message);
 
   // Helpers.
   bool RemoveClient(media::VideoCapture::EventHandler* handler,
                     ClientInfo* clients);
 
   const scoped_refptr<VideoCaptureMessageFilter> message_filter_;
-  const scoped_refptr<base::MessageLoopProxy> capture_message_loop_proxy_;
   const scoped_refptr<base::MessageLoopProxy> io_message_loop_proxy_;
   int device_id_;
   const int session_id_;
 
   // Buffers available for sending to the client.
   typedef std::map<int32, scoped_refptr<ClientBuffer> > ClientBufferMap;
   ClientBufferMap client_buffers_;
 
   ClientInfo clients_;
   ClientInfo clients_pending_on_filter_;
   ClientInfo clients_pending_on_restart_;
 
   // Member params_ represents the video format requested by the
-  // client to this class via DoStartCaptureOnCaptureThread.
+  // client to this class via StartCapture().
   media::VideoCaptureParams params_;
 
   // The device's video capture format sent from browser process side.
   media::VideoCaptureFormat last_frame_format_;
 
   bool suspended_;
   VideoCaptureState state_;
 
   // WeakPtrFactory pointing back to |this| object, for use with
   // media::VideoFrames constructed in OnBufferReceived() from buffers cached
   // in |client_buffers_|.
   base::WeakPtrFactory<VideoCaptureImpl> weak_this_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(VideoCaptureImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_VIDEO_CAPTURE_IMPL_H_