getUserMedia: handle the device starting status report.

content/renderer/media/media_stream_dispatcher.h

Index: content/renderer/media/media_stream_dispatcher.h
diff --git a/content/renderer/media/media_stream_dispatcher.h b/content/renderer/media/media_stream_dispatcher.h
index b5fc1d8210799f50d102d1feecce7e2177da0c2f..18803c1277de6a49f457159d4f794c91f45b42cc 100644
--- a/content/renderer/media/media_stream_dispatcher.h
+++ b/content/renderer/media/media_stream_dispatcher.h
@@ -72,6 +72,9 @@ class CONTENT_EXPORT MediaStreamDispatcher
   // Close a started device. |label| is provided in OnDeviceOpened.
   void CloseDevice(const std::string& label);
 
+  // This method is called when the stream is started successfully.
+  void OnStreamStarted(const std::string& label);
+
   // Check if the label is a valid stream.
   virtual bool IsStream(const std::string& label);
   // Get the video session_id given a label. The label identifies a stream.