Introduce isHTMLVideoElement and toHTMLVideoElement

Source/core/rendering/RenderVideo.cpp

 /*
  * Copyright (C) 2007, 2008, 2009, 2010 Apple 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 198 matching lines @@
     else
         mediaPlayer->paint(paintInfo.context, pixelSnappedIntRect(rect));
 }
 
 void RenderVideo::layout()
 {
     StackStats::LayoutCheckPoint layoutCheckPoint;
     RenderMedia::layout();
     updatePlayer();
 }
-    
+
 HTMLVideoElement* RenderVideo::videoElement() const
 {
-    ASSERT(node()->hasTagName(videoTag));
-    return static_cast<HTMLVideoElement*>(node()); 
+    ASSERT(isHTMLVideoElement(node()));
+    return toHTMLVideoElement(node());
 }
 
 void RenderVideo::updateFromElement()
 {
     RenderMedia::updateFromElement();
     updatePlayer();
 }
 
 void RenderVideo::updatePlayer()
 {
@@ skipping 68 matching lines @@
 }
 
 LayoutUnit RenderVideo::offsetHeight() const
 {
     if (const RenderBlock* block = rendererPlaceholder(this))
         return block->offsetHeight();
     return RenderMedia::offsetHeight();
 }
 
 } // namespace WebCore