Make Fullscreen::requestFullscreen and exitFullscreen static

third_party/WebKit/Source/core/dom/ElementFullscreen.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/dom/ElementFullscreen.h"
 
 #include "core/dom/Fullscreen.h"
 #include "core/frame/UseCounter.h"
 
 namespace blink {
 
 void ElementFullscreen::requestFullscreen(Element& element)
 {
-    Fullscreen::from(element.document()).requestFullscreen(element, Fullscreen::UnprefixedRequest);
+    Fullscreen::requestFullscreen(element, Fullscreen::UnprefixedRequest);
 }
 
 void ElementFullscreen::webkitRequestFullscreen(Element& element)
 {
     if (element.isInShadowTree())
         UseCounter::count(element.document(), UseCounter::PrefixedElementRequestFullscreenInShadow);
-    Fullscreen::from(element.document()).requestFullscreen(element, Fullscreen::PrefixedRequest);
+    Fullscreen::requestFullscreen(element, Fullscreen::PrefixedRequest);
 }
 
 } // namespace blink