Add video frame refresh to MediaStream and VideoCapture stacks.

content/renderer/media/media_stream_video_track.cc

 // Copyright 2013 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.
 
 #include "content/renderer/media/media_stream_video_track.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/location.h"
@@ skipping 194 matching lines @@
   track.setExtraData(new MediaStreamVideoTrack(source,
                                                constraints,
                                                callback,
                                                enabled));
   return track;
 }
 
 // static
 MediaStreamVideoTrack* MediaStreamVideoTrack::GetVideoTrack(
      const blink::WebMediaStreamTrack& track) {
+  if (track.isNull() ||
+      track.source().getType() != blink::WebMediaStreamSource::TypeVideo) {
+    return nullptr;
+  }
   return static_cast<MediaStreamVideoTrack*>(track.getExtraData());
 }
 
 MediaStreamVideoTrack::MediaStreamVideoTrack(
     MediaStreamVideoSource* source,
     const blink::WebMediaConstraints& constraints,
     const MediaStreamVideoSource::ConstraintsCallback& callback,
     bool enabled)
     : MediaStreamTrack(true),
       frame_deliverer_(
@@ skipping 53 matching lines @@
 }
 
 void MediaStreamVideoTrack::OnReadyStateChanged(
     blink::WebMediaStreamSource::ReadyState state) {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
   for (auto* sink : sinks_)
     sink->OnReadyStateChanged(state);
 }
 
 }  // namespace content