Add video frame refresh to MediaStream and VideoCapture stacks.

content/renderer/media/media_stream_video_track.cc

Index: content/renderer/media/media_stream_video_track.cc
diff --git a/content/renderer/media/media_stream_video_track.cc b/content/renderer/media/media_stream_video_track.cc
index 00e75faba188b6801f73a3f51218854afe3afb9a..9403e463d890a3bdba47c6185f640c9588ecf224 100644
--- a/content/renderer/media/media_stream_video_track.cc
+++ b/content/renderer/media/media_stream_video_track.cc
@@ -212,6 +212,10 @@ blink::WebMediaStreamTrack MediaStreamVideoTrack::CreateVideoTrack(
 // 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());
 }
 
@@ -247,9 +251,9 @@ void MediaStreamVideoTrack::AddSink(
   DCHECK(std::find(sinks_.begin(), sinks_.end(), sink) == sinks_.end());
   sinks_.push_back(sink);
   frame_deliverer_->AddCallback(sink, callback);
+
   // Request source to deliver a frame because a new sink is added.
-  if (source_)
-    source_->RequestRefreshFrame();
+  RequestRefreshFrame();
 }
 
 void MediaStreamVideoTrack::RemoveSink(MediaStreamVideoSink* sink) {
@@ -268,6 +272,12 @@ void MediaStreamVideoTrack::SetEnabled(bool enabled) {
     sink->OnEnabledChanged(enabled);
 }
 
+void MediaStreamVideoTrack::RequestRefreshFrame() {
+  DCHECK(main_render_thread_checker_.CalledOnValidThread());
+  if (source_)
+    source_->RequestRefreshFrame();
+}
+
 void MediaStreamVideoTrack::Stop() {
   DCHECK(main_render_thread_checker_.CalledOnValidThread());
   if (source_) {