Remove webkitIsFullScreen everywhere except in bindings

Source/core/dom/DocumentFullscreen.cpp

 /*
  * Copyright (C) 2013, 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 29 matching lines @@
     if (Fullscreen* fullscreen = Fullscreen::fromIfExists(document))
         return fullscreen->fullscreenElement();
     return 0;
 }
 
 void DocumentFullscreen::exitFullscreen(Document& document)
 {
     Fullscreen::from(document).exitFullscreen();
 }
 
-bool DocumentFullscreen::webkitIsFullScreen(Document& document)
-{
-    if (Fullscreen* fullscreen = Fullscreen::fromIfExists(document))
-        return fullscreen->webkitIsFullScreen();
-    return false;
-}
-
 bool DocumentFullscreen::webkitFullScreenKeyboardInputAllowed(Document& document)
 {
     if (Fullscreen* fullscreen = Fullscreen::fromIfExists(document))
         return fullscreen->webkitFullScreenKeyboardInputAllowed();
     return false;
 }
 
 Element* DocumentFullscreen::webkitCurrentFullScreenElement(Document& document)
 {
     if (Fullscreen* fullscreen = Fullscreen::fromIfExists(document))
         return fullscreen->webkitCurrentFullScreenElement();
     return 0;
 }
 
 } // namespace blink