Refactor video capturing code in the render process

content/renderer/media/media_stream_video_source.h

Index: content/renderer/media/media_stream_video_source.h
diff --git a/content/renderer/media/media_stream_video_source.h b/content/renderer/media/media_stream_video_source.h
index 5c5289dd776dd5864bbdd8187cb98d9a38419cd8..80889ce6c1a2178a31c88c324e57855019b7df4a 100644
--- a/content/renderer/media/media_stream_video_source.h
+++ b/content/renderer/media/media_stream_video_source.h
@@ -82,7 +82,12 @@ class CONTENT_EXPORT MediaStreamVideoSource
   // 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);
+  // |format| contains extra information like the frame rate of this source.
+  // |timestamp| is the time when the frame is generated. This field allows
+  // synchronization with other sources.
+  virtual void DeliverVideoFrame(const scoped_refptr<media::VideoFrame>& frame,
+                                 const media::VideoCaptureFormat& format,
+                                 const base::TimeTicks& timestamp);
 
   // An implementation must fetch the formats that can currently be used by
   // the source and call OnSupportedFormats when done.