Abort expensive AudioManager methods once shutdown starts.

media/audio/audio_manager_base.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_BASE_H_
 #define MEDIA_AUDIO_AUDIO_MANAGER_BASE_H_
 
 #include <string>
 #include <utility>
 
+#include "base/atomic_ref_count.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "base/observer_list.h"
 #include "base/threading/thread.h"
 #include "media/audio/audio_manager.h"
 
 #include "media/audio/audio_output_dispatcher.h"
 
 #if defined(OS_WIN)
@@ skipping 168 matching lines @@
   // and GetTaskRunner() starts returning NULL.
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
 
   // Map of cached AudioOutputDispatcher instances.  Must only be touched
   // from the audio thread (no locking).
   AudioOutputDispatchers output_dispatchers_;
 
   // Proxy for creating AudioLog objects.
   AudioLogFactory* const audio_log_factory_;
 
+  // Used to exit early from expensive methods after shutdown has started.
+  base::AtomicRefCount in_shutdown_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioManagerBase);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_MANAGER_BASE_H_