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

modules/audio_device/audio_device_generic.h

Index: modules/audio_device/audio_device_generic.h
diff --git a/modules/audio_device/audio_device_generic.h b/modules/audio_device/audio_device_generic.h
index 8f3e9dc00460a7526238621a93b0b934e5332aea..5679bd409341620b4cec662117752dd565c0d3aa 100644
--- a/modules/audio_device/audio_device_generic.h
+++ b/modules/audio_device/audio_device_generic.h
@@ -142,15 +142,6 @@ class AudioDeviceGeneric {
   virtual int GetRecordAudioParameters(AudioParameters* params) const;
 #endif  // WEBRTC_IOS
 
-  virtual bool PlayoutWarning() const = 0;
-  virtual bool PlayoutError() const = 0;
-  virtual bool RecordingWarning() const = 0;
-  virtual bool RecordingError() const = 0;
-  virtual void ClearPlayoutWarning() = 0;
-  virtual void ClearPlayoutError() = 0;
-  virtual void ClearRecordingWarning() = 0;
-  virtual void ClearRecordingError() = 0;
-
   virtual void AttachAudioBuffer(AudioDeviceBuffer* audioBuffer) = 0;
 
   virtual ~AudioDeviceGeneric() {}