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

voice_engine/voe_base_impl.h

Index: voice_engine/voe_base_impl.h
diff --git a/voice_engine/voe_base_impl.h b/voice_engine/voe_base_impl.h
index d03a1997c46f2d75bf96bbc54a6c83d50c0532ed..a3c4c1f40fbc63d4539e2c4d95b8e7d32fd954e8 100644
--- a/voice_engine/voe_base_impl.h
+++ b/voice_engine/voe_base_impl.h
@@ -22,8 +22,7 @@ namespace webrtc {
 class ProcessThread;
 
 class VoEBaseImpl : public VoEBase,
-                    public AudioTransport,
-                    public AudioDeviceObserver {
+                    public AudioTransport {
  public:
   int Init(
       AudioDeviceModule* external_adm,
@@ -81,10 +80,6 @@ class VoEBaseImpl : public VoEBase,
                                      int64_t* elapsed_time_ms,
                                      int64_t* ntp_time_ms) override;
 
-  // AudioDeviceObserver
-  void OnErrorIsReported(const ErrorCode error) override;
-  void OnWarningIsReported(const WarningCode warning) override;
-
  protected:
   VoEBaseImpl(voe::SharedData* shared);
   ~VoEBaseImpl() override;