Support external audio mixer.

webrtc/media/engine/webrtcvoe.h

 /*
  *  Copyright (c) 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 54 matching lines @@
   }
 
  private:
   T* ptr;
 };
 
 // Utility class for aggregating the various WebRTC interface.
 // Fake implementations can also be injected for testing.
 class VoEWrapper {
  public:
-  VoEWrapper()
-      : engine_(webrtc::VoiceEngine::Create()), processing_(engine_),
-        base_(engine_), codec_(engine_), hw_(engine_),
-        volume_(engine_) {
-  }
+  VoEWrapper(rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer)

[the sun, 2016/12/07 15:56:08]

AudioMixer has no business here.

[GeorgeZ, 2016/12/07 18:28:17]

Done.

+      : engine_(webrtc::VoiceEngine::Create()),
+        processing_(engine_),
+        base_(engine_),
+        codec_(engine_),
+        hw_(engine_),
+        volume_(engine_),
+        audio_mixer_(audio_mixer) {}
   VoEWrapper(webrtc::VoEAudioProcessing* processing,
              webrtc::VoEBase* base,
              webrtc::VoECodec* codec,
              webrtc::VoEHardware* hw,
              webrtc::VoEVolumeControl* volume)
       : engine_(NULL),
         processing_(processing),
         base_(base),
         codec_(codec),
         hw_(hw),
         volume_(volume) {
   }
   ~VoEWrapper() {}
   webrtc::VoiceEngine* engine() const { return engine_.get(); }
   webrtc::VoEAudioProcessing* processing() const { return processing_.get(); }
   webrtc::VoEBase* base() const { return base_.get(); }
   webrtc::VoECodec* codec() const { return codec_.get(); }
   webrtc::VoEHardware* hw() const { return hw_.get(); }
   webrtc::VoEVolumeControl* volume() const { return volume_.get(); }
   int error() { return base_->LastError(); }
+  rtc::scoped_refptr<webrtc::AudioMixer> AudioMixer() const {
+    return audio_mixer_;
+  }
 
  private:
   scoped_voe_engine engine_;
   scoped_voe_ptr<webrtc::VoEAudioProcessing> processing_;
   scoped_voe_ptr<webrtc::VoEBase> base_;
   scoped_voe_ptr<webrtc::VoECodec> codec_;
   scoped_voe_ptr<webrtc::VoEHardware> hw_;
   scoped_voe_ptr<webrtc::VoEVolumeControl> volume_;
+  rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer_ = nullptr;
 };
 }  // namespace cricket
 
 #endif  // WEBRTC_MEDIA_ENGINE_WEBRTCVOE_H_