Fix teardown of stale AudioStreamMonitor poll callbacks.

content/browser/media/audio_stream_monitor.h

Index: content/browser/media/audio_stream_monitor.h
diff --git a/content/browser/media/audio_stream_monitor.h b/content/browser/media/audio_stream_monitor.h
index ced46683efbfb3dcf17b91245bd65ac183fde2f4..8d773c8e49ccc38329d132a9a25b4dc4e5e44ee9 100644
--- a/content/browser/media/audio_stream_monitor.h
+++ b/content/browser/media/audio_stream_monitor.h
@@ -54,6 +54,10 @@ class CONTENT_EXPORT AudioStreamMonitor {
   // false as soon as the WebContents stop producing sound.
   bool IsCurrentlyAudible() const;
 
+  // Called by the WebContentsImpl if |render_process_id| dies; used to clear
+  // any outstanding poll callbacks.
+  void RenderProcessGone(int render_process_id);
+
   // Starts or stops audio level monitoring respectively for the stream owned by
   // the specified renderer.  Safe to call from any thread.
   //