Move the device enumerate/open/close work to device thread from IO thread

content/browser/renderer_host/media/audio_input_device_manager.h

Index: content/browser/renderer_host/media/audio_input_device_manager.h
diff --git a/content/browser/renderer_host/media/audio_input_device_manager.h b/content/browser/renderer_host/media/audio_input_device_manager.h
index 96bff65679102dd59554b1e2d057e1223cf1c2c6..2911ac2da9dcfe8bfa9c88d58d4190081b79183a 100644
--- a/content/browser/renderer_host/media/audio_input_device_manager.h
+++ b/content/browser/renderer_host/media/audio_input_device_manager.h
@@ -6,8 +6,8 @@
 // communicates with MediaStreamManager and AudioInputRendererHost on the
 // browser IO thread, handles queries like enumerate/open/close from
 // MediaStreamManager and start/stop from AudioInputRendererHost.
-
-// All the queries and work are handled on the IO thread.
+// The work for enumerate/open/close is handled asynchronously on Media Stream
+// device thread, while start/stop are synchronous API on IO thread.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_INPUT_DEVICE_MANAGER_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_INPUT_DEVICE_MANAGER_H_
@@ -41,7 +41,7 @@ class CONTENT_EXPORT AudioInputDeviceManager
   static const int kInvalidSessionId;
   static const char kInvalidDeviceId[];
 
-  explicit AudioInputDeviceManager(media::AudioManager* audio_manager);
+  AudioInputDeviceManager(scoped_refptr<base::MessageLoopProxy> message_loop);
 
   // MediaStreamProvider implementation, called on IO thread.
   virtual void Register(MediaStreamProviderListener* listener) OVERRIDE;
@@ -57,24 +57,42 @@ class CONTENT_EXPORT AudioInputDeviceManager
   // Stop the device referenced by the session id.
   void Stop(int session_id);
 
+  // Used by unit test.
+  void SetAudioManagerForTesting(media::AudioManager* audio_manager);
+
  private:
   friend class base::RefCountedThreadSafe<AudioInputDeviceManager>;
   virtual ~AudioInputDeviceManager();
 
+  // Executed on media stream device thread.
+  void EnumerateOnDeviceThread();
+  void OpenOnDeviceThread(int session_id, const StreamDeviceInfo& device);
+  void CloseOnDeviceThread(int session_id);
+
   // Executed on IO thread to call Listener.
   void DevicesEnumeratedOnIOThread(StreamDeviceInfoArray* devices);
   void OpenedOnIOThread(int session_id);
   void ClosedOnIOThread(int session_id);
   void ErrorOnIOThread(int session_id, MediaStreamProviderError error);
 
+  // Helpers.
+  bool IsOnDeviceThread() const;
+
+  // Only accessed on Browser::IO thread.
   MediaStreamProviderListener* listener_;
   int next_capture_session_id_;
   typedef std::map<int, AudioInputDeviceManagerEventHandler*> EventHandlerMap;
   EventHandlerMap event_handlers_;
+
+  // Only accessed from media stream device thread.
   typedef std::map<int, media::AudioDeviceName> AudioInputDeviceMap;
   AudioInputDeviceMap devices_;
-  // TODO(tommi): Is it necessary to store this as a member?
-  media::AudioManager* audio_manager_;
+
+  // The message loop of media stream device thread that this object runs on.
+  scoped_refptr<base::MessageLoopProxy> message_loop_;
+
+  // AudioManager for testing.
+  media::AudioManager* testing_audio_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioInputDeviceManager);
 };