Revert of Pass task runners to AudioManager constructor.

media/audio/mac/audio_manager_mac.h

Index: media/audio/mac/audio_manager_mac.h
diff --git a/media/audio/mac/audio_manager_mac.h b/media/audio/mac/audio_manager_mac.h
index f8c99e80dfb749c01cd689223c955e02fed2b8ab..c1105387763ac51e4c4cdf85327c41d87c3af86f 100644
--- a/media/audio/mac/audio_manager_mac.h
+++ b/media/audio/mac/audio_manager_mac.h
@@ -26,12 +26,11 @@
 // the AudioManager class.
 class MEDIA_EXPORT AudioManagerMac : public AudioManagerBase {
  public:
-  AudioManagerMac(
-      scoped_refptr<base::SingleThreadTaskRunner> task_runner,
-      scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner,
-      AudioLogFactory* audio_log_factory);
+  AudioManagerMac(AudioLogFactory* audio_log_factory);
 
   // Implementation of AudioManager.
+  scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunner() override;
+  scoped_refptr<base::SingleThreadTaskRunner> GetWorkerTaskRunner() override;
   bool HasAudioOutputDevices() override;
   bool HasAudioInputDevices() override;
   void GetAudioInputDeviceNames(AudioDeviceNames* device_names) override;
@@ -118,6 +117,7 @@
 
  private:
   void InitializeOnAudioThread();
+  void ShutdownOnAudioThread();
 
   int ChooseBufferSize(bool is_input, int sample_rate);
 
@@ -126,6 +126,9 @@
   void HandleDeviceChanges();
 
   scoped_ptr<AudioDeviceListenerMac> output_device_listener_;
+
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  scoped_ptr<base::Thread> worker_thread_;
 
   // Track the output sample-rate and the default output device
   // so we can intelligently handle device notifications only when necessary.
@@ -138,11 +141,8 @@
   class AudioPowerObserver;
   scoped_ptr<AudioPowerObserver> power_observer_;
 
-  // Tracks all constructed input and output streams.
-  // TODO(alokp): We used to track these streams to close before destruction.
-  // We no longer close the streams, so we may be able to get rid of these
-  // member variables. They are currently used by MaybeChangeBufferSize().
-  // Investigate if we can remove these.
+  // Tracks all constructed input and output streams so they can be stopped at
+  // shutdown.  See ShutdownOnAudioThread() for more details.
   std::list<AudioInputStream*> basic_input_streams_;
   std::list<AUAudioInputStream*> low_latency_input_streams_;
   std::list<AUHALStream*> output_streams_;