Support external audio mixer.

webrtc/api/peerconnectionfactory.h

 /*
  *  Copyright 2011 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 93 matching lines @@
  protected:
   PeerConnectionFactory();
   PeerConnectionFactory(
       rtc::Thread* network_thread,
       rtc::Thread* worker_thread,
       rtc::Thread* signaling_thread,
       AudioDeviceModule* default_adm,
       const rtc::scoped_refptr<webrtc::AudioDecoderFactory>&
           audio_decoder_factory,
       cricket::WebRtcVideoEncoderFactory* video_encoder_factory,
-      cricket::WebRtcVideoDecoderFactory* video_decoder_factory);
+      cricket::WebRtcVideoDecoderFactory* video_decoder_factory,
+      rtc::scoped_refptr<AudioMixer> audio_mixer);
   virtual ~PeerConnectionFactory();
 
  private:
   cricket::MediaEngineInterface* CreateMediaEngine_w();
 
   bool owns_ptrs_;
   bool wraps_current_thread_;
   rtc::Thread* network_thread_;
   rtc::Thread* worker_thread_;
   rtc::Thread* signaling_thread_;
   Options options_;
   // External Audio device used for audio playback.
   rtc::scoped_refptr<AudioDeviceModule> default_adm_;
   rtc::scoped_refptr<AudioDecoderFactory> audio_decoder_factory_;
   std::unique_ptr<cricket::ChannelManager> channel_manager_;
   // External Video encoder factory. This can be NULL if the client has not
   // injected any. In that case, video engine will use the internal SW encoder.
   std::unique_ptr<cricket::WebRtcVideoEncoderFactory> video_encoder_factory_;
   // External Video decoder factory. This can be NULL if the client has not
   // injected any. In that case, video engine will use the internal SW decoder.
   std::unique_ptr<cricket::WebRtcVideoDecoderFactory> video_decoder_factory_;
   std::unique_ptr<rtc::BasicNetworkManager> default_network_manager_;
   std::unique_ptr<rtc::BasicPacketSocketFactory> default_socket_factory_;
+  rtc::scoped_refptr<AudioMixer> external_audio_mixer_;

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

Please add comment describing what happens if this is nullptr.

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

Done.

 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_PEERCONNECTIONFACTORY_H_