Support external audio mixer.

webrtc/media/base/mediaengine.h

Index: webrtc/media/base/mediaengine.h
diff --git a/webrtc/media/base/mediaengine.h b/webrtc/media/base/mediaengine.h
index 8083c8edaccd6ea1ef2a9c8a2b3dfce1618b1695..505a9b10c894c5688963563dff0e9af82e04298b 100644
--- a/webrtc/media/base/mediaengine.h
+++ b/webrtc/media/base/mediaengine.h
@@ -18,6 +18,7 @@
 #include <string>
 #include <vector>
 
+#include "webrtc/api/audio/audio_mixer.h"
 #include "webrtc/api/call/audio_state.h"
 #include "webrtc/api/rtpparameters.h"
 #include "webrtc/base/fileutils.h"
@@ -110,11 +111,11 @@ class MediaEngineFactory {
 template<class VOICE, class VIDEO>
 class CompositeMediaEngine : public MediaEngineInterface {
  public:
-  CompositeMediaEngine(
-      webrtc::AudioDeviceModule* adm,
-      const rtc::scoped_refptr<webrtc::AudioDecoderFactory>&
-          audio_decoder_factory)
-      : voice_(adm, audio_decoder_factory) {}
+  CompositeMediaEngine(webrtc::AudioDeviceModule* adm,
+                       const rtc::scoped_refptr<webrtc::AudioDecoderFactory>&
+                           audio_decoder_factory,
+                       rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer)
+      : voice_(adm, audio_decoder_factory, audio_mixer) {}
   virtual ~CompositeMediaEngine() {}
   virtual bool Init() {
     video_.Init();