Refactor video capturing code in the render process

content/renderer/media/media_stream_video_source.h

 // Copyright 2014 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 CONTENT_RENDERER_MEDIA_MEDIA_STREAM_VIDEO_SOURCE_H_
 #define CONTENT_RENDERER_MEDIA_MEDIA_STREAM_VIDEO_SOURCE_H_
 
 #include <vector>
 
 #include "base/compiler_specific.h"
@@ skipping 64 matching lines @@
 
  protected:
   virtual void DoStopSource() OVERRIDE;
 
   // Sets ready state and notifies the ready state to all registered tracks.
   virtual void SetReadyState(blink::WebMediaStreamSource::ReadyState state);
 
   // Delivers |frame| to registered tracks according to their constraints.
   // Note: current implementation assumes |frame| be contiguous layout of image
   // planes and I420.
-  virtual void DeliverVideoFrame(const scoped_refptr<media::VideoFrame>& frame);
+  virtual void DeliverVideoFrame(const scoped_refptr<media::VideoFrame>& frame,
+                                 const media::VideoCaptureFormat& format,
+                                 const base::TimeTicks& timestamp);

[Ami GONE FROM CHROMIUM, 2014/04/24 21:04:31]

media::VideoFrame has a timestamp field.  Why is this timestamp param required
here in addition?
(requires a comment at least)

[Alpha Left Google, 2014/04/24 22:50:34]

Done.

[Alpha Left Google, 2014/04/24 22:50:34]

It is there to allow synchronization with other sources. Added a comment.

 
   // An implementation must fetch the formats that can currently be used by
   // the source and call OnSupportedFormats when done.
   // |max_requested_height| and |max_requested_width| is the max height and
   // width set as a mandatory constraint if set when calling
   // MediaStreamVideoSource::AddTrack. If max height and max width is not set
   // |max_requested_height| and |max_requested_width| are 0.
   virtual void GetCurrentSupportedFormats(int max_requested_width,
                                           int max_requested_height) = 0;
   void OnSupportedFormats(const media::VideoCaptureFormats& formats);
@@ skipping 67 matching lines @@
 
   // Tracks that currently are receiving video frames.
   std::vector<MediaStreamVideoTrack*> tracks_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaStreamVideoSource);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_VIDEO_SOURCE_H_