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..3134829559fdf90c991b33d595eb64afcfe89218 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());
 }
 
@@ -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_) {