Change VideoTrack implementation to invoke VideoTrackSourceInterface::AddOrUpdateSink on wt

webrtc/api/mediastreaminterface.h

Index: webrtc/api/mediastreaminterface.h
diff --git a/webrtc/api/mediastreaminterface.h b/webrtc/api/mediastreaminterface.h
index 2acaa000e4898ca1f2c067d1b605b5561d42d406..b1d25f68adfa5e639ab30a556a65af3c69b6b201 100644
--- a/webrtc/api/mediastreaminterface.h
+++ b/webrtc/api/mediastreaminterface.h
@@ -105,6 +105,11 @@ class MediaStreamTrackInterface : public rtc::RefCountInterface,
 
 // VideoTrackSourceInterface is a reference counted source used for
 // VideoTracks. The same source can be used by multiple VideoTracks.
+// VideoTrackSourceInterface is designed to be invoked on the signaling thread
+// except for rtc::VideoSourceInterface<VideoFrame> methods that will be invoked
+// on the worker thread via a VideoTrack. A custom implementation of a source
+// can inherit AdaptedVideoTrackSource instead of directly implementing this
+// interface.
 class VideoTrackSourceInterface
     : public MediaSourceInterface,
       public rtc::VideoSourceInterface<VideoFrame> {
@@ -139,6 +144,12 @@ class VideoTrackSourceInterface
   virtual ~VideoTrackSourceInterface() {}
 };
 
+// VideoTrackInterface is designed to be invoked on the signaling thread except
+// for rtc::VideoSourceInterface<VideoFrame> methods that must be invoked
+// on the worker thread.
+// PeerConnectionFactory::CreateVideoTrack can be used for creating a VideoTrack
+// that ensures thread safety and that all methods are called on the right
+// thread.
 class VideoTrackInterface
     : public MediaStreamTrackInterface,
       public rtc::VideoSourceInterface<VideoFrame> {
@@ -148,12 +159,6 @@ class VideoTrackInterface
   // See https://crbug.com/653531 and https://github.com/WICG/mst-content-hint.
   enum class ContentHint { kNone, kFluid, kDetailed };
 
-  // Register a video sink for this track. Used to connect the track to the
-  // underlying video engine.
-  void AddOrUpdateSink(rtc::VideoSinkInterface<VideoFrame>* sink,
-                       const rtc::VideoSinkWants& wants) override {}
-  void RemoveSink(rtc::VideoSinkInterface<VideoFrame>* sink) override {}
-
   virtual VideoTrackSourceInterface* GetSource() const = 0;
 
   virtual ContentHint content_hint() const { return ContentHint::kNone; }