Improve caption button behavior for video player.

third_party/WebKit/Source/core/html/shadow/MediaControls.h

 /*
  * Copyright (C) 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 43 matching lines @@
   void beginScrubbing();
   void endScrubbing();
 
   void updateCurrentTimeDisplay();
 
   void updateVolume();
 
   void changedClosedCaptionsVisibility();
   void refreshClosedCaptionsButtonVisibility();
   void toggleTextTrackList();
+  void showTextTrackAtIndex(unsigned indexToEnable);
+  void disableShowingTextTracks();
 
   void enteredFullscreen();
   void exitedFullscreen();
 
   void startedCasting();
   void stoppedCasting();
   void refreshCastButtonVisibility();
   void showOverlayCastButtonIfNeeded();
   // Update cast button visibility, but don't try to update our panel
   // button visibility for space.
@@ skipping 97 matching lines @@
   int m_panelWidth;
 
   bool m_allowHiddenVolumeControls : 1;
 };
 
 DEFINE_ELEMENT_TYPE_CASTS(MediaControls, isMediaControls());
 
 }  // namespace blink
 
 #endif