getUserMedia: handle the device starting status report.

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.
 
 #ifndef CONTENT_RENDERER_MEDIA_VIDEO_CAPTURE_IMPL_H_
 #define CONTENT_RENDERER_MEDIA_VIDEO_CAPTURE_IMPL_H_
 
 #include <stdint.h>
 
 #include <list>
@@ skipping 133 matching lines @@
   // Video format requested by the client to this class via StartCapture().
   media::VideoCaptureParams params_;
 
   // First captured frame reference time sent from browser process side.
   base::TimeTicks first_frame_ref_time_;
 
   VideoCaptureState state_;
 
   base::ThreadChecker io_thread_checker_;
 
+  // Flag set to True when captured frames are dropped due to arriving earlier
+  // than OnStarted event. Then a frame refresh request will be sent out later
+  // when OnStarted arrives, for a new frame to start the video call with.
+  // This only has effect on screen capture.
+  bool maybe_refresh_frame_;

[chfremer, 2017/03/02 17:56:10]

The "maybe_" prefix seems redundant, since it is clear that the bool may be true
or false. I recommend naming this "should_request_refresh_frame_on_started_".

The comment "This only has effect on screen capture." is a dangerous claim to
make here, because it assumes knowledge of what happens outside of this class. I
understand that you want to document the effect on the larger context, but this
is not a good location for putting this information, because when the larger
context changes, who will know that there is documentation hiding in here that
needs to be updated?

[braveyao, 2017/03/03 17:53:12]

Done.

+
   // WeakPtrFactory pointing back to |this| object, for use with
   // media::VideoFrames constructed in OnBufferReceived() from buffers cached
   // in |client_buffers_|.
   base::WeakPtrFactory<VideoCaptureImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(VideoCaptureImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_VIDEO_CAPTURE_IMPL_H_