Support external audio mixer.

webrtc/media/engine/webrtcmediaengine.h

 /*
  *  Copyright (c) 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.
  */
 
 #ifndef WEBRTC_MEDIA_ENGINE_WEBRTCMEDIAENGINE_H_
 #define WEBRTC_MEDIA_ENGINE_WEBRTCMEDIAENGINE_H_
 
 #include <string>
 #include <vector>
 
 #include "webrtc/config.h"
 #include "webrtc/media/base/mediaengine.h"
 
 namespace webrtc {
 class AudioDecoderFactory;
 class AudioDeviceModule;
+class AudioMixer;
 }
 namespace cricket {
 class WebRtcVideoDecoderFactory;
 class WebRtcVideoEncoderFactory;
 }
 
 namespace cricket {
 
 class WebRtcMediaEngineFactory {
  public:
   // TODO(ossu): Backwards-compatible interface. Will be deprecated once the
   // audio decoder factory is fully plumbed and used throughout WebRTC.
   // See: crbug.com/webrtc/6000
   static MediaEngineInterface* Create(
       webrtc::AudioDeviceModule* adm,
       WebRtcVideoEncoderFactory* video_encoder_factory,
-      WebRtcVideoDecoderFactory* video_decoder_factory);
+      WebRtcVideoDecoderFactory* video_decoder_factory,
+      rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer);

[the sun, 2016/12/12 20:50:05]

is this version of the function actually used with the AudioMixer argument? if
not, revert the change to it, or you'll probably break downstream.

[GeorgeZ, 2016/12/13 00:16:42]

Thanks for point this out.

 
   static MediaEngineInterface* Create(
       webrtc::AudioDeviceModule* adm,
       const rtc::scoped_refptr<webrtc::AudioDecoderFactory>&
           audio_decoder_factory,
       WebRtcVideoEncoderFactory* video_encoder_factory,
-      WebRtcVideoDecoderFactory* video_decoder_factory);
+      WebRtcVideoDecoderFactory* video_decoder_factory,
+      rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer);
 };
 
 // Verify that extension IDs are within 1-byte extension range and are not
 // overlapping.
 bool ValidateRtpExtensions(const std::vector<webrtc::RtpExtension>& extensions);
 
 // Discard any extensions not validated by the 'supported' predicate. Duplicate
 // extensions are removed if 'filter_redundant_extensions' is set, and also any
 // mutually exclusive extensions (see implementation for details) are removed.
 std::vector<webrtc::RtpExtension> FilterRtpExtensions(
     const std::vector<webrtc::RtpExtension>& extensions,
     bool (*supported)(const std::string&),
     bool filter_redundant_extensions);
 
 }  // namespace cricket
 
 #endif  // WEBRTC_MEDIA_ENGINE_WEBRTCMEDIAENGINE_H_