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

modules/include/module.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 40 matching lines @@
   //     running.
   //   * ProcessThread::Stop() was called and the thread has been stopped.
   //
   // NOTE: This method is not called from the worker thread itself, but from
   //       the thread that registers/deregisters the module or calls Start/Stop.
   virtual void ProcessThreadAttached(ProcessThread* process_thread) {}
 
  protected:
   virtual ~Module() {}
 };
-
-// Reference counted version of the Module interface.
-class RefCountedModule : public Module {
- public:
-  // Increase the reference count by one.
-  // Returns the incremented reference count.
-  virtual int32_t AddRef() const = 0;
-
-  // Decrease the reference count by one.
-  // Returns the decreased reference count.
-  // Returns 0 if the last reference was just released.
-  // When the reference count reaches 0 the object will self-destruct.
-  virtual int32_t Release() const = 0;
-
- protected:
-  ~RefCountedModule() override = default;
-};
-
 }  // namespace webrtc
 
 #endif  // MODULES_INCLUDE_MODULE_H_