Cast: deliver video frames on the IO thread

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 c65803622036e6b8c502ddde7403e7c39a07f560..af874e29076cda384b814027e3d015ba5fd929e6 100644
--- a/content/public/renderer/media_stream_video_sink.cc
+++ b/content/public/renderer/media_stream_video_sink.cc
@@ -12,11 +12,12 @@ namespace content {
 
 void MediaStreamVideoSink::AddToVideoTrack(
     MediaStreamVideoSink* sink,
+    const VideoSinkDeliverFrameCB& callback,
     const blink::WebMediaStreamTrack& track) {
   DCHECK_EQ(blink::WebMediaStreamSource::TypeVideo, track.source().type());
   MediaStreamVideoTrack* video_track =
       static_cast<MediaStreamVideoTrack*>(track.extraData());
-  video_track->AddSink(sink);
+  video_track->AddSink(sink, callback);
 }
 
 void MediaStreamVideoSink::RemoveFromVideoTrack(