Revert of 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 96b5019701bdc1ee9046c6a8f766d4bd37496bc0..8083c8edaccd6ea1ef2a9c8a2b3dfce1618b1695 100644
--- a/webrtc/media/base/mediaengine.h
+++ b/webrtc/media/base/mediaengine.h
@@ -33,7 +33,6 @@
 
 namespace webrtc {
 class AudioDeviceModule;
-class AudioMixer;
 class Call;
 }
 
@@ -111,11 +110,11 @@
 template<class VOICE, class VIDEO>
 class CompositeMediaEngine : public MediaEngineInterface {
  public:
-  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) {}
+  CompositeMediaEngine(
+      webrtc::AudioDeviceModule* adm,
+      const rtc::scoped_refptr<webrtc::AudioDecoderFactory>&
+          audio_decoder_factory)
+      : voice_(adm, audio_decoder_factory) {}
   virtual ~CompositeMediaEngine() {}
   virtual bool Init() {
     video_.Init();