Introduce CancelUponDeferral() to buffered media loaders.

media/blink/buffered_data_source.h

Index: media/blink/buffered_data_source.h
diff --git a/media/blink/buffered_data_source.h b/media/blink/buffered_data_source.h
index b047c19a52e76da4261988d61ee04ac97f77dbad..fcfb6b06f5fe3a46cbc4e121c8d1140fea29a39e 100644
--- a/media/blink/buffered_data_source.h
+++ b/media/blink/buffered_data_source.h
@@ -103,10 +103,15 @@ class MEDIA_EXPORT BufferedDataSource : public DataSource {
   void MediaPlaybackRateChanged(float playback_rate);
   void MediaIsPlaying();
   void MediaIsPaused();
+  bool media_has_played() const { return media_has_played_; }
 
   // Returns true if the resource is local.
   bool assume_fully_buffered() { return !url_.SchemeIsHTTPOrHTTPS(); }
 
+  // Cancels any open network connections once reaching the deferred state. If
+  // the DataSource is already deferred connections will be immediately closed.
+  void CancelUponDeferral();
+
   // DataSource implementation.
   // Called from demuxer thread.
   void Stop() override;