Change DtmfSenderHandler to handle events on the signaling thread.

content/renderer/media/webrtc/media_stream_remote_video_source.cc

Index: content/renderer/media/webrtc/media_stream_remote_video_source.cc
diff --git a/content/renderer/media/webrtc/media_stream_remote_video_source.cc b/content/renderer/media/webrtc/media_stream_remote_video_source.cc
index c9cb883af843142e012053f3fe11d1b5d2112eac..873b0af3aaf2aab316b41c27e058a5098e95b84f 100644
--- a/content/renderer/media/webrtc/media_stream_remote_video_source.cc
+++ b/content/renderer/media/webrtc/media_stream_remote_video_source.cc
@@ -131,7 +131,10 @@ RemoteVideoSourceDelegate::DoRenderFrameOnIOThread(
 MediaStreamRemoteVideoSource::Observer::Observer(
     const scoped_refptr<base::SingleThreadTaskRunner>& main_thread,
     webrtc::VideoTrackInterface* track)
-    : main_thread_(main_thread), track_(track), state_(track->state()) {
+    : main_thread_(main_thread),
+      source_set_(false),
+      track_(track),
+      state_(track->state()) {
   track->RegisterObserver(this);
 }
 
@@ -156,11 +159,18 @@ void MediaStreamRemoteVideoSource::Observer::SetSource(
     const base::WeakPtr<MediaStreamRemoteVideoSource>& source) {
   DCHECK(main_thread_->BelongsToCurrentThread());
   DCHECK(!source_);
+  DLOG(ERROR) << "SetSource";

[tommi (sloooow) - chröme, 2014/11/03 13:49:56]

remove? (and the rest of the debug logging)

[perkj_chrome, 2014/11/03 14:53:33]

sorry....

   source_ = source;
+  // |source_set_| means that there is a MediaStreamRemoteVideoSource that
+  // should handle all state changes. Since an Observer is always created when
+  // a remote MediaStream changes in RemoteMediaStreamImpl::Observer::OnChanged,
+  // it can happen that an Observer is created but SetSource is never called.
+  source_set_ = true;
 }
 
 void MediaStreamRemoteVideoSource::Observer::OnChanged() {
   webrtc::MediaStreamTrackInterface::TrackState state = track_->state();
+  DLOG(ERROR) << ":Observer::OnChanged" << state;
   main_thread_->PostTask(FROM_HERE,
       base::Bind(&MediaStreamRemoteVideoSource::Observer::OnChangedImpl,
           this, state));
@@ -169,7 +179,7 @@ void MediaStreamRemoteVideoSource::Observer::OnChanged() {
 void MediaStreamRemoteVideoSource::Observer::OnChangedImpl(
     webrtc::MediaStreamTrackInterface::TrackState state) {
   DCHECK(main_thread_->BelongsToCurrentThread());
-  DCHECK(source_) << "Dropping a state change event. " << state;
+  DCHECK(source_ || !source_set_) << "Dropping a state change event. " << state;
   if (source_ && state != state_)
     source_->OnChanged(state);
   state_ = state;
@@ -179,9 +189,11 @@ MediaStreamRemoteVideoSource::MediaStreamRemoteVideoSource(
     const scoped_refptr<MediaStreamRemoteVideoSource::Observer>& observer)
     : observer_(observer), weak_factory_(this) {
   observer->SetSource(weak_factory_.GetWeakPtr());
+  DLOG(ERROR) << "MediaStreamRemoteVideoSource";
 }
 
 MediaStreamRemoteVideoSource::~MediaStreamRemoteVideoSource() {
+  DLOG(ERROR) << "~MediaStreamRemoteVideoSource";
   DCHECK(CalledOnValidThread());
 }
 
@@ -221,6 +233,7 @@ MediaStreamRemoteVideoSource::RenderInterfaceForTest() {
 void MediaStreamRemoteVideoSource::OnChanged(
     webrtc::MediaStreamTrackInterface::TrackState state) {
   DCHECK(CalledOnValidThread());
+  DLOG(ERROR) << "OnChanged" << state;
   switch (state) {
     case webrtc::MediaStreamTrackInterface::kInitializing:
       // Ignore the kInitializing state since there is no match in