Remove AudioDeviceObserver and make ADM not inherit from the Module interface.

modules/audio_device/include/fake_audio_device.h

 /*
  *  Copyright (c) 2013 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 MODULES_AUDIO_DEVICE_INCLUDE_FAKE_AUDIO_DEVICE_H_
 #define MODULES_AUDIO_DEVICE_INCLUDE_FAKE_AUDIO_DEVICE_H_
 
 #include "modules/audio_device/include/audio_device.h"
 
 namespace webrtc {
 
 class FakeAudioDeviceModule : public AudioDeviceModule {
  public:
   FakeAudioDeviceModule() {}
   virtual ~FakeAudioDeviceModule() {}
   virtual int32_t AddRef() const { return 0; }
   virtual int32_t Release() const { return 0; }
 
  private:
-  virtual int32_t RegisterEventObserver(AudioDeviceObserver* eventCallback) {
-    return 0;
-  }
   virtual int32_t RegisterAudioCallback(AudioTransport* audioCallback) {
     return 0;
   }
   virtual int32_t Init() { return 0; }
   virtual int32_t InitSpeaker() { return 0; }
   virtual int32_t SetPlayoutDevice(uint16_t index) { return 0; }
   virtual int32_t SetPlayoutDevice(WindowsDeviceType device) { return 0; }
   virtual int32_t SetStereoPlayout(bool enable) { return 0; }
   virtual int32_t StopPlayout() { return 0; }
   virtual int32_t InitMicrophone() { return 0; }
@@ skipping 108 matching lines @@
 #endif  // WEBRTC_IOS
 
  private:
   bool uses_default_module_implementation_ = false;
   bool turn_off_module_callbacks_ = false;
 };
 
 }  // namespace webrtc
 
 #endif  // MODULES_AUDIO_DEVICE_INCLUDE_FAKE_AUDIO_DEVICE_H_