Media Remoting: Add interstitial elements to media element shadow dom.

third_party/WebKit/public/platform/WebMediaPlayerClient.h

Index: third_party/WebKit/public/platform/WebMediaPlayerClient.h
diff --git a/third_party/WebKit/public/platform/WebMediaPlayerClient.h b/third_party/WebKit/public/platform/WebMediaPlayerClient.h
index 301fad6740c77972017863e4e974b45da68230cd..35d5db595f05ce6b68c8e0a8271674ad943ba7f4 100644
--- a/third_party/WebKit/public/platform/WebMediaPlayerClient.h
+++ b/third_party/WebKit/public/platform/WebMediaPlayerClient.h
@@ -116,6 +116,10 @@ class BLINK_PLATFORM_EXPORT WebMediaPlayerClient {
   // Returns the selected video track id (or an empty id if there's none).
   virtual WebMediaPlayer::TrackId GetSelectedVideoTrackId() = 0;
 
+  // Informs that media starts/stops being rendered and played back remotely.
+  virtual void MediaRemotingStarted() {}
+  virtual void MediaRemotingStopped() {}
+
  protected:
   ~WebMediaPlayerClient() {}
 };