Send kStopMark from AudioOutputController to stop AudioThread in renderer

media/audio/audio_output_controller.h

Index: media/audio/audio_output_controller.h
===================================================================
--- media/audio/audio_output_controller.h	(revision 131586)
+++ media/audio/audio_output_controller.h	(working copy)
@@ -80,6 +80,10 @@
   // indicating that the stream is paused.
   static const int kPauseMark;
 
+  // M18-specific hack for crbug.com/121141: value sent to the renderer in
+  // low-latency mode telling the renderer to close the socket.
+  static const int kStopMark;
+
   // An event handler that receives events from the AudioOutputController. The
   // following methods are called on the audio controller thread.
   class MEDIA_EXPORT EventHandler {