Make WebRtcVideoChannel2::WebRtcVideoSendStream implement rtc::VideoRendererInterface.

talk/app/webrtc/rtpsender.cc

Index: talk/app/webrtc/rtpsender.cc
diff --git a/talk/app/webrtc/rtpsender.cc b/talk/app/webrtc/rtpsender.cc
index 72a9114eb4df315dcdbd85e1fdc792ad3ddb704d..293b3600754ee0dd456fa4bea4c44e476376c1f0 100644
--- a/talk/app/webrtc/rtpsender.cc
+++ b/talk/app/webrtc/rtpsender.cc
@@ -268,9 +268,17 @@ bool VideoRtpSender::SetTrack(MediaStreamTrackInterface* track) {
   }
   VideoTrackInterface* video_track = static_cast<VideoTrackInterface*>(track);
 
+  // TODO(nisse): To make code a little simpler, ensure that
+  // GetSink(0) returns NULL, and that AddSink and RemoveSink with
+  // NULL is safe.
+  rtc::VideoSinkInterface<cricket::VideoFrame>* sink =
+      provider_->GetSink(ssrc_);
+
   // Detach from old track.
   if (track_) {
     track_->UnregisterObserver(this);
+    if (sink)
+      track_->RemoveSink(sink);
   }
 
   // Attach to new track.
@@ -279,6 +287,8 @@ bool VideoRtpSender::SetTrack(MediaStreamTrackInterface* track) {
   if (track_) {
     cached_track_enabled_ = track_->enabled();
     track_->RegisterObserver(this);
+    if (sink)
+      video_track->AddSink(sink);
   }
 
   // Update video provider.
@@ -325,6 +335,14 @@ void VideoRtpSender::Stop() {
   }
   if (track_) {
     track_->UnregisterObserver(this);
+
+    rtc::VideoSinkInterface<cricket::VideoFrame>* sink =
+        provider_->GetSink(ssrc_);
+    if (sink)
+      track_->RemoveSink(sink);
+    else
+      LOG(LS_ERROR)
+          << "VideoRtpSender::Stop called with a NULL sink. Too late???";

[perkj_webrtc, 2016/01/26 15:40:56]

Is there ever a case when this is fine? If not- I think we should remove the if
(sink) to catch the error.

[nisse-webrtc, 2016/01/28 08:24:53]

I think track_->RemoveSink(nullptr) will succeed and do nothing (and I think
that makes some sense). So to catch the error, I think we have to check for it
here. Possibly using RTC_CHECK?

   }
   if (can_send_track()) {
     provider_->SetCaptureDevice(ssrc_, nullptr);