Decouple 'give me more data' and 'rendered end of stream' audio callbacks.

media/filters/audio_renderer_base.cc

Index: media/filters/audio_renderer_base.cc
===================================================================
--- media/filters/audio_renderer_base.cc	(revision 121128)
+++ media/filters/audio_renderer_base.cc	(working copy)
@@ -272,8 +272,10 @@
 }
 
 void AudioRendererBase::SignalEndOfStream() {
-  DCHECK(recieved_end_of_stream_);
-  if (!rendered_end_of_stream_) {
+  // Lock, there is potential race condition on
+  // |recieved_end_of_stream_| and |rendered_end_of_stream_|.
+  base::AutoLock auto_lock(lock_);
+  if (recieved_end_of_stream_ && !rendered_end_of_stream_) {
     rendered_end_of_stream_ = true;
     host()->NotifyEnded();
   }