Add test to make sure if PPB_Audio_Shared::StartThread() works.

ppapi/shared_impl/ppb_audio_shared.h

Index: ppapi/shared_impl/ppb_audio_shared.h
diff --git a/ppapi/shared_impl/ppb_audio_shared.h b/ppapi/shared_impl/ppb_audio_shared.h
index 6ba8cac2e669135d8593070dc8b5ab5f045be9b2..59913a0085078b901a0c1a7455b5815d26a99886 100644
--- a/ppapi/shared_impl/ppb_audio_shared.h
+++ b/ppapi/shared_impl/ppb_audio_shared.h
@@ -67,7 +67,7 @@ class PPAPI_SHARED_EXPORT PPB_Audio_Shared
   // configures our object to stop generating callbacks. The actual stop
   // playback request will be done in the derived classes and will be different
   // from the proxy and the renderer.
-  void SetStartPlaybackState();
+  bool SetStartPlaybackState();
   void SetStopPlaybackState();
 
   // Sets the shared memory and socket handles. This will automatically start
@@ -87,7 +87,7 @@ class PPAPI_SHARED_EXPORT PPB_Audio_Shared
 
  private:
   // Starts execution of the audio thread.
-  void StartThread();
+  bool StartThread();
 
   // Stop execution of the audio thread.
   void StopThread();