Refactor VideoTracks to forward all sinks to its source

webrtc/media/base/videobroadcaster.h

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_MEDIA_BASE_VIDEOBROADCASTER_H_
 #define WEBRTC_MEDIA_BASE_VIDEOBROADCASTER_H_
 
 #include <utility>
 #include <vector>
 
 #include "webrtc/base/criticalsection.h"
 #include "webrtc/base/thread_checker.h"
 #include "webrtc/media/base/videoframe.h"
 #include "webrtc/media/base/videosinkinterface.h"
 #include "webrtc/media/base/videosourceinterface.h"
+#include "webrtc/media/engine/webrtcvideoframe.h"
 
 namespace rtc {
 
 // VideoBroadcaster broadcast video frames to sinks and combines
 // VideoSinkWants from its sinks. It does that by implementing
 // rtc::VideoSourceInterface and rtc::VideoSinkInterface.
 // Sinks must be added and removed on one and only one thread.
 // Video frames can be broadcasted on any thread. I.e VideoBroadcaster::OnFrame
 // can be called on any thread.
 class VideoBroadcaster : public VideoSourceInterface<cricket::VideoFrame>,
@@ skipping 17 matching lines @@
   struct SinkPair {
     SinkPair(VideoSinkInterface<cricket::VideoFrame>* sink,
              VideoSinkWants wants)
         : sink(sink), wants(wants) {}
     VideoSinkInterface<cricket::VideoFrame>* sink;
     VideoSinkWants wants;
   };
   SinkPair* FindSinkPair(const VideoSinkInterface<cricket::VideoFrame>* sink)
       EXCLUSIVE_LOCKS_REQUIRED(sinks_and_wants_lock_);
   void UpdateWants() EXCLUSIVE_LOCKS_REQUIRED(sinks_and_wants_lock_);
+  const cricket::VideoFrame& GetBlackFrame(const cricket::VideoFrame& frame)
+      EXCLUSIVE_LOCKS_REQUIRED(sinks_and_wants_lock_);
 
   ThreadChecker thread_checker_;
   rtc::CriticalSection sinks_and_wants_lock_;
 
   VideoSinkWants current_wants_ GUARDED_BY(sinks_and_wants_lock_);
   std::vector<SinkPair> sinks_ GUARDED_BY(sinks_and_wants_lock_);
+
+  rtc::scoped_ptr<cricket::WebRtcVideoFrame> black_frame_;
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_MEDIA_BASE_VIDEOBROADCASTER_H_