Makes AudioOutputProxy -> AudioOutputDispatcher reference weak.

media/audio/audio_output_proxy.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_AUDIO_AUDIO_OUTPUT_PROXY_H_
 #define MEDIA_AUDIO_AUDIO_OUTPUT_PROXY_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "base/threading/non_thread_safe.h"
 #include "media/audio/audio_io.h"
 #include "media/base/audio_parameters.h"
 
 namespace media {
 
 class AudioOutputDispatcher;
 
 // AudioOutputProxy is an audio otput stream that uses resources more
 // efficiently than a regular audio output stream: it opens audio
 // device only when sound is playing, i.e. between Start() and Stop()
 // (there is still one physical stream per each audio output proxy in
 // playing state).
 //
 // AudioOutputProxy uses AudioOutputDispatcher to open and close
 // physical output streams.
 class MEDIA_EXPORT AudioOutputProxy
   : public AudioOutputStream,
     public NON_EXPORTED_BASE(base::NonThreadSafe) {
  public:
   // Caller keeps ownership of |dispatcher|.
-  explicit AudioOutputProxy(AudioOutputDispatcher* dispatcher);
+  explicit AudioOutputProxy(base::WeakPtr<AudioOutputDispatcher> dispatcher);
 
   // AudioOutputStream interface.
   bool Open() override;
   void Start(AudioSourceCallback* callback) override;
   void Stop() override;
   void SetVolume(double volume) override;
   void GetVolume(double* volume) override;
   void Close() override;
 
   AudioOutputDispatcher* get_dispatcher_for_testing() const {
-    return dispatcher_;
+    return dispatcher_.get();
   }
 
  private:
   enum State {
     kCreated,
     kOpened,
     kPlaying,
     kClosed,
     kOpenError,
     kStartError,
   };
 
   ~AudioOutputProxy() override;
 
-  AudioOutputDispatcher* dispatcher_;
+  base::WeakPtr<AudioOutputDispatcher> dispatcher_;
   State state_;
 
   // Need to save volume here, so that we can restore it in case the stream
   // is stopped, and then started again.
   double volume_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioOutputProxy);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_PROXY_H_