Refactor AudioInputDevice to remove race conditions and allow more flexible calling sequences.

content/renderer/media/audio_input_device.h

Index: content/renderer/media/audio_input_device.h
===================================================================
--- content/renderer/media/audio_input_device.h	(revision 97438)
+++ content/renderer/media/audio_input_device.h	(working copy)
@@ -59,6 +59,9 @@
 
 // TODO(henrika): This class is based on the AudioDevice class and it has
 // many components in common. Investigate potential for re-factoring.
+// TODO(henrika): Add support for event handling (e.g. OnStateChanged,
+// OnCaptureStopped etc.) and ensure that we can deliver these notifications
+// to any clients using this class.
 class AudioInputDevice
     : public AudioInputMessageFilter::Delegate,
       public base::DelegateSimpleThread::Delegate,
@@ -80,8 +83,8 @@
                    CaptureCallback* callback);
   virtual ~AudioInputDevice();
 
-  // Starts audio capturing. Returns |true| on success.
-  bool Start();
+  // Starts audio capturing.
+  void Start();
 
   // Stops audio capturing. Returns |true| on success.
   bool Stop();
@@ -111,7 +114,7 @@
   // sends IPC messages on that thread.
   void InitializeOnIOThread(const AudioParameters& params);
   void StartOnIOThread();
-  void ShutDownOnIOThread();
+  void ShutDownOnIOThread(base::WaitableEvent* completion);
   void SetVolumeOnIOThread(double volume);
 
   void Send(IPC::Message* message);