Remove the AudioManager singleton.

media/audio/audio_manager_base.h

Index: media/audio/audio_manager_base.h
===================================================================
--- media/audio/audio_manager_base.h	(revision 113173)
+++ media/audio/audio_manager_base.h	(working copy)
@@ -7,6 +7,7 @@
 
 #include <map>
 
+#include "base/atomic_ref_count.h"
 #include "base/compiler_specific.h"
 #include "base/threading/thread.h"
 #include "media/audio/audio_manager.h"
@@ -23,8 +24,15 @@
 
   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 void Cleanup() OVERRIDE;
 
   virtual MessageLoop* GetMessageLoop() OVERRIDE;
 
@@ -43,33 +51,32 @@
 
   void IncreaseActiveInputStreamCount();
   void DecreaseActiveInputStreamCount();
+  void Shutdown();
 
  protected:
   virtual ~AudioManagerBase();
 
+  // The map holds a weak reference to the AudioOutputDispatcher objects
+  // to avoid circular dependencies.  When the dispatcher dies, it notifies
+  // us via ClearOutputDispatcher.
   typedef std::map<AudioParameters, scoped_refptr<AudioOutputDispatcher>,
                    AudioParameters::Compare>
       AudioOutputDispatchersMap;
 
-  bool initialized() { return initialized_; }
+  void ShutdownOnAudioThread();
 
+  bool initialized() { return audio_thread_.IsRunning(); }
+
   // Thread used to interact with AudioOutputStreams created by this
   // audio manger.
   base::Thread audio_thread_;
 
-  bool initialized_;
-
   AudioOutputDispatchersMap output_dispatchers_;
 
   // Counts the number of active input streams to find out if something else
   // is currently recording in Chrome.
-  int num_active_input_streams_;
+  base::AtomicRefCount num_active_input_streams_;
 
-  // Lock used to synchronize the access to num_active_input_streams_.
-  // Do not use for anything else and try to avoid using other locks
-  // in this code whenever possible.
-  base::Lock active_input_streams_lock_;
-
   DISALLOW_COPY_AND_ASSIGN(AudioManagerBase);
 };