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

media/audio/audio_manager_base.h

 // Copyright (c) 2011 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_BASE_H_
 #define MEDIA_AUDIO_AUDIO_MANAGER_BASE_H_
 
 #include <map>
 
 #include "base/atomic_ref_count.h"
 #include "base/compiler_specific.h"
-#include "base/threading/thread.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/synchronization/lock.h"
 #include "media/audio/audio_manager.h"
 
 class AudioOutputDispatcher;
 
+namespace base {
+class Thread;
+}
+
 // AudioManagerBase provides AudioManager functions common for all platforms.
 class MEDIA_EXPORT AudioManagerBase : public AudioManager {
  public:
   // Name of the generic "default" device.
   static const char kDefaultDeviceName[];
   // Unique Id of the generic "default" device.
   static const char kDefaultDeviceId[];
 
   AudioManagerBase();
 
 #ifndef NDEBUG
   // Overridden to make sure we don't accidentally get added reference counts on
   // the audio thread.  The AudioManagerBase instance must always be deleted
   // from outside the audio thread.
   virtual void AddRef() const OVERRIDE;
   virtual void Release() const OVERRIDE;
 #endif
 
   virtual void Init() OVERRIDE;
 
-  virtual MessageLoop* GetMessageLoop() OVERRIDE;
+  virtual scoped_refptr<base::MessageLoopProxy> GetMessageLoop() OVERRIDE;
 
   virtual string16 GetAudioInputDeviceModel() OVERRIDE;
 
   virtual bool CanShowAudioInputSettings() OVERRIDE;
   virtual void ShowAudioInputSettings() OVERRIDE;
 
   virtual void GetAudioInputDeviceNames(media::AudioDeviceNames* device_names)
       OVERRIDE;
 
   virtual AudioOutputStream* MakeAudioOutputStreamProxy(
@@ skipping 11 matching lines @@
 
  protected:
   virtual ~AudioManagerBase();
 
   typedef std::map<AudioParameters, scoped_refptr<AudioOutputDispatcher>,
                    AudioParameters::Compare>
       AudioOutputDispatchersMap;
 
   void ShutdownOnAudioThread();
 
-  bool initialized() { return audio_thread_.IsRunning(); }
-
   // Thread used to interact with AudioOutputStreams created by this
   // audio manger.
-  base::Thread audio_thread_;
+  scoped_ptr<base::Thread> audio_thread_;
+  mutable base::Lock audio_thread_lock_;
 
+  // Map of cached AudioOutputDispatcher instances.  Must only be touched
+  // from the audio thread (no locking).
   AudioOutputDispatchersMap output_dispatchers_;
 
   // Counts the number of active input streams to find out if something else
   // is currently recording in Chrome.
   base::AtomicRefCount num_active_input_streams_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioManagerBase);
 };
 
 #endif  // MEDIA_AUDIO_AUDIO_MANAGER_BASE_H_