Change VideoRtpReceiver to create remote VideoTrack and VideoTrackSource.

webrtc/media/base/videobroadcaster.cc

Index: webrtc/media/base/videobroadcaster.cc
diff --git a/webrtc/media/base/videobroadcaster.cc b/webrtc/media/base/videobroadcaster.cc
index 5fa3db733bbb66d410d3b2f8bf230c5d498cf83f..015f5206b676e239666e4fa5f374ebecb2a0270c 100644
--- a/webrtc/media/base/videobroadcaster.cc
+++ b/webrtc/media/base/videobroadcaster.cc
@@ -25,6 +25,7 @@ void VideoBroadcaster::AddOrUpdateSink(
     const VideoSinkWants& wants) {
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
   RTC_DCHECK(sink != nullptr);
+  rtc::CritScope cs(&sinks_and_wants_lock_);
 
   SinkPair* sink_pair = FindSinkPair(sink);
   if (!sink_pair) {
@@ -39,8 +40,8 @@ void VideoBroadcaster::RemoveSink(
     VideoSinkInterface<cricket::VideoFrame>* sink) {
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
   RTC_DCHECK(sink != nullptr);
+  rtc::CritScope cs(&sinks_and_wants_lock_);
   RTC_DCHECK(FindSinkPair(sink));
-
   sinks_.erase(std::remove_if(sinks_.begin(), sinks_.end(),
                               [sink](const SinkPair& sink_pair) {
                                 return sink_pair.sink == sink;
@@ -51,16 +52,18 @@ void VideoBroadcaster::RemoveSink(
 
 bool VideoBroadcaster::frame_wanted() const {
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
+  rtc::CritScope cs(&sinks_and_wants_lock_);
   return !sinks_.empty();
 }
 
 VideoSinkWants VideoBroadcaster::wants() const {
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
+  rtc::CritScope cs(&sinks_and_wants_lock_);
   return current_wants_;
 }
 
 void VideoBroadcaster::OnFrame(const cricket::VideoFrame& frame) {
-  RTC_DCHECK(thread_checker_.CalledOnValidThread());
+  rtc::CritScope cs(&sinks_and_wants_lock_);
   for (auto& sink_pair : sinks_) {
     sink_pair.sink->OnFrame(frame);
   }