Implemented the GetSources() in native code.

webrtc/pc/rtpreceiver.h

 /*
  *  Copyright 2015 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 12 matching lines @@
 #include "webrtc/api/rtpreceiverinterface.h"
 #include "webrtc/base/basictypes.h"
 #include "webrtc/base/sigslot.h"
 #include "webrtc/media/base/videobroadcaster.h"
 #include "webrtc/pc/channel.h"
 #include "webrtc/pc/remoteaudiosource.h"
 #include "webrtc/pc/videotracksource.h"
 
 namespace webrtc {
 
+class RtpContributingSource;
+
 // Internal class used by PeerConnection.
 class RtpReceiverInternal : public RtpReceiverInterface {
  public:
   virtual void Stop() = 0;
   // This SSRC is used as an identifier for the receiver between the API layer
   // and the WebRtcVideoEngine2, WebRtcVoiceEngine layer.
   virtual uint32_t ssrc() const = 0;
+
+  // TODO(zhihuang): Remove the default implemenation once the subclasses

[Taylor Brandstetter, 2017/03/30 22:55:38]

nit: Spelling of "implementation"

Also, isn't the default implementation needed on RtpReceiverInterface, not
RtpReceiverInternal? And, assuming the only relevant subclass is
"FakeRtpReceiver" in chromium, it may be helpful to mention it by name, as a
reminder to whoever goes to fix the TODO.

[Zhi Huang, 2017/03/31 06:44:05]

Done.

+  // implement this.
+  virtual std::vector<std::unique_ptr<RtpContributingSourceInterface>>
+  GetContributingSources() {
+    return std::vector<std::unique_ptr<RtpContributingSourceInterface>>();
+  }
 };
 
 class AudioRtpReceiver : public ObserverInterface,
                          public AudioSourceInterface::AudioObserver,
                          public rtc::RefCountedObject<RtpReceiverInternal>,
                          public sigslot::has_slots<> {
  public:
   // An SSRC of 0 will create a receiver that will match the first SSRC it
   // sees.
   // TODO(deadbeef): Use rtc::Optional, or have another constructor that
@@ skipping 31 matching lines @@
   // RtpReceiverInternal implementation.
   void Stop() override;
   uint32_t ssrc() const override { return ssrc_; }
 
   void SetObserver(RtpReceiverObserverInterface* observer) override;
 
   // Does not take ownership.
   // Should call SetChannel(nullptr) before |channel| is destroyed.
   void SetChannel(cricket::VoiceChannel* channel);
 
+  std::vector<std::unique_ptr<RtpContributingSourceInterface>>
+  GetContributingSources() override;
+
  private:
   void Reconfigure();
   void OnFirstPacketReceived(cricket::BaseChannel* channel);
 
   const std::string id_;
   const uint32_t ssrc_;
   cricket::VoiceChannel* channel_;
   const rtc::scoped_refptr<AudioTrackInterface> track_;
   bool cached_track_enabled_;
   double cached_volume_ = 1;
@@ skipping 57 matching lines @@
   rtc::scoped_refptr<VideoTrackSource> source_;
   rtc::scoped_refptr<VideoTrackInterface> track_;
   bool stopped_ = false;
   RtpReceiverObserverInterface* observer_ = nullptr;
   bool received_first_packet_ = false;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_PC_RTPRECEIVER_H_