Share one thread between all AudioOutputControllers instead of creating one per stream.

media/audio/audio_output_controller.h

 // Copyright (c) 2010 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_CONTROLLER_H_
 #define MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_
 
 #include "base/lock.h"
 #include "base/ref_counted.h"
 #include "base/scoped_ptr.h"
-#include "base/thread.h"
 #include "base/time.h"
 #include "media/audio/audio_io.h"
+#include "media/audio/audio_manager.h"
 #include "media/audio/simple_sources.h"
 
+class MessageLoop;
+
 // An AudioOutputController controls an AudioOutputStream and provides data
 // to this output stream. It has an important function that it executes
 // audio operations like play, pause, stop, etc. on a separate thread,
 // namely the audio controller thread.
 //
 // All the public methods of AudioOutputController are non-blocking except
 // close, the actual operations are performed on the audio controller thread.
 //
 // Here is a state diagram for the AudioOutputController:
 //
@@ skipping 105 matching lines @@
   // Starts the playback of this audio output stream.
   void Play();
 
   // Pause this audio output stream.
   void Pause();
 
   // Discard all audio data buffered in this output stream. This method only
   // has effect when the stream is paused.
   void Flush();
 
-  // Closes the audio output stream and shutdown the audio controller thread.
-  // This method returns only after all operations are completed. This
-  // controller cannot be used after this method is called.
+  // Closes the audio output stream. It changes state to kClosed and returns
+  // right away. The physical resources are freed on the audio thread if
+  // neccessary.
   //
   // It is safe to call this method more than once. Calls after the first one
   // will have no effect.
   void Close();
 
   // Sets the volume of the audio output stream.
   void SetVolume(double volume);
 
   // Enqueue audio |data| into the controller. This method is used only in
   // the regular latency mode and it is illegal to call this method when
@@ skipping 42 matching lines @@
   base::Time last_callback_time_;
   Lock lock_;
 
   // PushSource role is to buffer and it's only used in regular latency mode.
   PushSource push_source_;
   uint32 buffer_capacity_;
 
   // SyncReader is used only in low latency mode for synchronous reading.
   SyncReader* sync_reader_;
 
-  // The audio controller thread that this object runs on.
-  base::Thread thread_;
+  // The message loop of audio thread that this object runs on.
+  MessageLoop* message_loop_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioOutputController);
 };
 
 }  // namespace media
 
 #endif  //  MEDIA_AUDIO_AUDIO_OUTPUT_CONTROLLER_H_