MediaStream: Adding VideoTrackRecorder class and unittests

content/public/renderer/media_stream_video_sink.cc

Index: content/public/renderer/media_stream_video_sink.cc
diff --git a/content/public/renderer/media_stream_video_sink.cc b/content/public/renderer/media_stream_video_sink.cc
index 6ca37c584a191f1afd1cd0a9f85237e4c339c8ec..efd38ea93513bb515d4778c8da3001a68a53b8db 100644
--- a/content/public/renderer/media_stream_video_sink.cc
+++ b/content/public/renderer/media_stream_video_sink.cc
@@ -15,7 +15,7 @@ void MediaStreamVideoSink::AddToVideoTrack(
     const VideoCaptureDeliverFrameCB& callback,
     const blink::WebMediaStreamTrack& track) {
   DCHECK_EQ(blink::WebMediaStreamSource::TypeVideo, track.source().type());
-  MediaStreamVideoTrack* video_track =
+  MediaStreamVideoTrack* const video_track =
       static_cast<MediaStreamVideoTrack*>(track.extraData());
   video_track->AddSink(sink, callback);
 }
@@ -24,7 +24,7 @@ void MediaStreamVideoSink::RemoveFromVideoTrack(
     MediaStreamVideoSink* sink,
     const blink::WebMediaStreamTrack& track) {
   DCHECK_EQ(blink::WebMediaStreamSource::TypeVideo, track.source().type());
-  MediaStreamVideoTrack* video_track =
+  MediaStreamVideoTrack* const video_track =
       static_cast<MediaStreamVideoTrack*>(track.extraData());
   video_track->RemoveSink(sink);
 }