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

modules/audio_device/audio_device_impl.h

 /*
  *  Copyright (c) 2012 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.
  */
 
@@ skipping 26 matching lines @@
     kPlatformIOS = 6
   };
 
   int32_t CheckPlatform();
   int32_t CreatePlatformSpecificObjects();
   int32_t AttachAudioBuffer();
 
   AudioDeviceModuleImpl(const int32_t id, const AudioLayer audioLayer);
   ~AudioDeviceModuleImpl() override;
 
-  int64_t TimeUntilNextProcess() override;
-  void Process() override;
-
   // Retrieve the currently utilized audio layer
   int32_t ActiveAudioLayer(AudioLayer* audioLayer) const override;
 
   // Error handling
   ErrorCode LastError() const override;
-  int32_t RegisterEventObserver(AudioDeviceObserver* eventCallback) override;
 
   // Full-duplex transportation of PCM audio
   int32_t RegisterAudioCallback(AudioTransport* audioCallback) override;
 
   // Main initializaton and termination
   int32_t Init() override;
   int32_t Terminate() override;
   bool Initialized() const override;
 
   // Device enumeration
@@ skipping 105 matching lines @@
     return _audioManagerAndroid.get();
   }
 #endif
   AudioDeviceBuffer* GetAudioDeviceBuffer() { return &_audioDeviceBuffer; }
 
  private:
   PlatformType Platform() const;
   AudioLayer PlatformAudioLayer() const;
 
   rtc::CriticalSection _critSect;
-  rtc::CriticalSection _critSectEventCb;
   rtc::CriticalSection _critSectAudioCb;
 
-  AudioDeviceObserver* _ptrCbAudioDeviceObserver;
-
   AudioDeviceGeneric* _ptrAudioDevice;
 
   AudioDeviceBuffer _audioDeviceBuffer;
 #if defined(WEBRTC_ANDROID)
   std::unique_ptr<AudioManager> _audioManagerAndroid;
 #endif
   int32_t _id;
   AudioLayer _platformAudioLayer;
-  int64_t _lastProcessTime;
   PlatformType _platformType;
   bool _initialized;
   mutable ErrorCode _lastError;
 };
 
 }  // namespace webrtc
 
 #endif  // defined(WEBRTC_INCLUDE_INTERNAL_AUDIO_DEVICE)
 
 #endif  // MODULES_INTERFACE_AUDIO_DEVICE_IMPL_H_