Refactor video capturing code in the render process

content/renderer/media/webrtc/video_destination_handler.cc

Index: content/renderer/media/webrtc/video_destination_handler.cc
diff --git a/content/renderer/media/webrtc/video_destination_handler.cc b/content/renderer/media/webrtc/video_destination_handler.cc
index ac16f1e693b0e96e3a74ff5dd28b36943e8ca107..bec6febd4d8567ea8d4a3ce3c4018e4f89865a43 100644
--- a/content/renderer/media/webrtc/video_destination_handler.cc
+++ b/content/renderer/media/webrtc/video_destination_handler.cc
@@ -116,7 +116,9 @@ void PpFrameWriter::PutFrame(PPB_ImageData_Impl* image_data,
                      new_frame->stride(media::VideoFrame::kVPlane),
                      frame_size.width(), frame_size.height());
 
-  DeliverVideoFrame(new_frame);
+  // TODO(hclam): Should take into account |timestamp|.
+  // Not all sinks care about the TimeTicks so it's not a problem now.

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

ditto comment elsewhere, why wouldn't you use |timestamp| from l.98?

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

The parameter is a TimeTicks. I would need to save a start time to compute the
correct TimeTicks here.

The reason for using TimeTicks: it is a Chrome wide clock that allows
synchronization of streams. Our camera implementations already provide this but
we drop it in VideoCaptureImpl. I'm adding this back to the interface.

Non-camera implementation of sources can just give TimeTicks::Now().

[Ami GONE FROM CHROMIUM, 2014/04/24 23:05:18]

I'm unclear on why synchronization can't be done using media::VideoFrame's
TimeDeltas (and a per-stream start TimeTicks, which would have to be maintained
by whoever is doing the synchronizing).

[Alpha Left Google, 2014/04/24 23:33:53]

When a frame is captured in the browser. It is tagged with a TimeTicks (Moment
A). Current code in tree trims this to a TimeDelta and set it to VideoFrame in
VCI. Downstream code currently record a stream start TimeTicks (Moment B) and
add the TimeDelta back to obtain a time for synchronization. 

There is a latency between moment A and B. It would be better to just pass along
the TimeTicks untouched.

+  DeliverVideoFrame(new_frame, format_, base::TimeTicks::Now());
 }
 
 // PpFrameWriterProxy is a helper class to make sure the user won't use
@@ -190,4 +192,3 @@ bool VideoDestinationHandler::Open(
 }
 
 }  // namespace content
-