Propagate MediaStreamSource state to video tracks the same way as audio.

webrtc/api/videotrack.cc

Index: webrtc/api/videotrack.cc
diff --git a/webrtc/api/videotrack.cc b/webrtc/api/videotrack.cc
index 54c3cce91a11d084ee99b475c53149fe66f53e37..bd380254b2d0e5ab7ab961152799b9ba4c33af16 100644
--- a/webrtc/api/videotrack.cc
+++ b/webrtc/api/videotrack.cc
@@ -20,9 +20,11 @@ VideoTrack::VideoTrack(const std::string& label,
                        VideoTrackSourceInterface* video_source)
     : MediaStreamTrack<VideoTrackInterface>(label),
       video_source_(video_source) {
+  video_source_->RegisterObserver(this);
 }
 
 VideoTrack::~VideoTrack() {
+  video_source_->UnregisterObserver(this);
 }
 
 std::string VideoTrack::kind() const {
@@ -56,6 +58,15 @@ bool VideoTrack::set_enabled(bool enable) {
   return MediaStreamTrack<VideoTrackInterface>::set_enabled(enable);
 }
 
+void VideoTrack::OnChanged() {
+  RTC_DCHECK(thread_checker_.CalledOnValidThread());
+  if (video_source_->state() == MediaSourceInterface::kEnded) {
+    set_state(kEnded);
+  } else {
+    set_state(kLive);
+  }
+}
+
 rtc::scoped_refptr<VideoTrack> VideoTrack::Create(
     const std::string& id,
     VideoTrackSourceInterface* source) {