Add thread safety to AudioManagerBase to protect access to the audio thread member variable.

media/audio/audio_manager.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_MANAGER_H_
 #define MEDIA_AUDIO_AUDIO_MANAGER_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "base/string16.h"
 #include "media/audio/audio_device_name.h"
 #include "media/audio/audio_parameters.h"
 
 class AudioInputStream;
 class AudioOutputStream;
 class MessageLoop;
+namespace base {
+class MessageLoopProxy;
+}
 
 // Manages all audio resources. In particular it owns the AudioOutputStream
 // objects. Provides some convenience functions that avoid the need to provide
 // iterators over the existing streams.
 // TODO(tommi): Make the manager non-refcounted when it's safe to do so.
 // -> Bug 107087.
 class MEDIA_EXPORT AudioManager
     : public base::RefCountedThreadSafe<AudioManager> {
  public:
   AudioManager();
@@ skipping 85 matching lines @@
 
   // Muting continues playback but effectively the volume is set to zero.
   // Un-muting returns the volume to the previous level.
   virtual void MuteAll() = 0;
   virtual void UnMuteAll() = 0;
 
   // Used to determine if something else is currently making use of audio input.
   virtual bool IsRecordingInProcess() = 0;
 
   // Returns message loop used for audio IO.
-  virtual MessageLoop* GetMessageLoop() = 0;
+  virtual scoped_refptr<base::MessageLoopProxy> GetMessageLoop() = 0;
 
  protected:
   // Called from Create() to initialize the instance.
   virtual void Init() = 0;
 
   friend class base::RefCountedThreadSafe<AudioManager>;
   virtual ~AudioManager();
 };
 
 #endif  // MEDIA_AUDIO_AUDIO_MANAGER_H_