Added audio mixer and removed audio device module in AudioState::Config.

webrtc/api/call/audio_state.h

Index: webrtc/api/call/audio_state.h
diff --git a/webrtc/api/call/audio_state.h b/webrtc/api/call/audio_state.h
index ac912773aa5fdeb12a59120b794c269605614050..1941cbf7bcd976c8aaabdf24709e6440d41443ac 100644
--- a/webrtc/api/call/audio_state.h
+++ b/webrtc/api/call/audio_state.h
@@ -10,6 +10,7 @@
 #ifndef WEBRTC_API_CALL_AUDIO_STATE_H_
 #define WEBRTC_API_CALL_AUDIO_STATE_H_
 
+#include "webrtc/api/audio/audio_mixer.h"
 #include "webrtc/base/refcount.h"
 #include "webrtc/base/scoped_ref_ptr.h"
 
@@ -33,8 +34,9 @@ class AudioState : public rtc::RefCountInterface {
     // the AudioState itself.
     VoiceEngine* voice_engine = nullptr;
 
-    // The AudioDeviceModule associated with the Calls.
-    AudioDeviceModule* audio_device_module = nullptr;
+    // The audio mixer connected to active receive streams. One per
+    // AudioState.
+    rtc::scoped_refptr<AudioMixer> audio_mixer;
   };
 
   // TODO(solenberg): Replace scoped_refptr with shared_ptr once we can use it.