Implemented the GetSources() in native code.

webrtc/pc/channel.cc

 /*
  *  Copyright 2004 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.
  */
 
@@ skipping 1645 matching lines @@
 bool VoiceChannel::SetRtpReceiveParameters_w(uint32_t ssrc,
                                              webrtc::RtpParameters parameters) {
   return media_channel()->SetRtpReceiveParameters(ssrc, parameters);
 }
 
 bool VoiceChannel::GetStats(VoiceMediaInfo* stats) {
   return InvokeOnWorker(RTC_FROM_HERE, Bind(&VoiceMediaChannel::GetStats,
                                             media_channel(), stats));
 }
 
+std::vector<webrtc::RtpContributingSource*>
+VoiceChannel::GetContributingSources(uint32_t ssrc) {
+  return worker_thread()->Invoke<std::vector<webrtc::RtpContributingSource*>>(
+      RTC_FROM_HERE,
+      Bind(&VoiceMediaChannel::GetContributingSources, media_channel(), ssrc));

[Zhi Huang, 2017/03/31 06:44:04]

I'll downcast this instead of adding the method to the basic class because there
would be circular dependency between the rtpreceiveritnerface.h and
mediachannel.h.

+}
+
 void VoiceChannel::StartMediaMonitor(int cms) {
   media_monitor_.reset(new VoiceMediaMonitor(media_channel(), worker_thread(),
       rtc::Thread::Current()));
   media_monitor_->SignalUpdate.connect(
       this, &VoiceChannel::OnMediaMonitorUpdate);
   media_monitor_->Start(cms);
 }
 
 void VoiceChannel::StopMediaMonitor() {
   if (media_monitor_) {
@@ skipping 789 matching lines @@
   signaling_thread()->Post(RTC_FROM_HERE, this, MSG_READYTOSENDDATA,
                            new DataChannelReadyToSendMessageData(writable));
 }
 
 void RtpDataChannel::GetSrtpCryptoSuites_n(
     std::vector<int>* crypto_suites) const {
   GetSupportedDataCryptoSuites(crypto_options(), crypto_suites);
 }
 
 }  // namespace cricket