Support external audio mixer.

webrtc/api/peerconnection.h

 /*
  *  Copyright 2012 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 127 matching lines @@
 
   void RegisterUMAObserver(UMAObserver* observer) override;
 
   bool StartRtcEventLog(rtc::PlatformFile file,
                         int64_t max_size_bytes) override;
   void StopRtcEventLog() override;
 
   void Close() override;
 
   sigslot::signal1<DataChannel*> SignalDataChannelCreated;
+  std::vector<uint32_t> GetRemoteAudioTrackSsrcs() override;

[aleloi, 2016/12/05 14:03:08]

Is there problems with implementing this in client-code through a
PeerConnectionObserver instead?

[GeorgeZ, 2016/12/05 17:56:18]

Functions in PeerConnectionObserver are event/callbacks functions to response
the state changes of Peerconnection. GetRemoteAudioTrackSsrcs() is more a state
inquire/get function and not fit in the event/callback function category. Since
PeerconnectionInterface has many get functions, I guess it may be a better place
to put GetRemoteAudioTrackSsrcs() into.

 
   // Virtual for unit tests.
   virtual const std::vector<rtc::scoped_refptr<DataChannel>>&
   sctp_data_channels() const {
     return sctp_data_channels_;
   }
 
  protected:
   ~PeerConnection() override;
 
@@ skipping 270 matching lines @@
       rtc::scoped_refptr<RtpReceiverProxyWithInternal<RtpReceiverInternal>>>
       receivers_;
   std::unique_ptr<WebRtcSession> session_;
   std::unique_ptr<StatsCollector> stats_;
   rtc::scoped_refptr<RTCStatsCollector> stats_collector_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_PEERCONNECTION_H_