Implement the unprefixed the Fullscreen API

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 "config.h"
 #include "core/dom/ElementFullscreen.h"
 
 #include "core/dom/FullscreenElementStack.h"
 
 namespace blink {
 
+void ElementFullscreen::requestFullscreen(Element& element)
+{
+    FullscreenElementStack::from(element.document()).requestFullscreen(element, FullscreenElementStack::UnprefixedRequest);
+}
+
 void ElementFullscreen::webkitRequestFullscreen(Element& element)
 {
     FullscreenElementStack::from(element.document()).requestFullscreen(element, FullscreenElementStack::PrefixedRequest);
 }
 
 void ElementFullscreen::webkitRequestFullScreen(Element& element, unsigned short flags)
 {
     FullscreenElementStack::RequestType requestType;
     if (flags & ALLOW_KEYBOARD_INPUT)
         requestType = FullscreenElementStack::PrefixedMozillaAllowKeyboardInputRequest;
     else
         requestType = FullscreenElementStack::PrefixedMozillaRequest;
     FullscreenElementStack::from(element.document()).requestFullscreen(element, requestType);
 }
 
 } // namespace blink