Introduce toHTMLIFrameElement

Source/core/rendering/RenderIFrame.cpp

 /*
  * Copyright (C) 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 60 matching lines @@
 
     RenderView* childRoot = contentRootRenderer();
     if (!childRoot)
         return 0;
 
     return childRoot->maxPreferredLogicalWidth() + borderAndPaddingLogicalWidth();
 }
 
 bool RenderIFrame::isSeamless() const
 {
-    return node() && node()->hasTagName(iframeTag) && static_cast<HTMLIFrameElement*>(node())->shouldDisplaySeamlessly();
+    return node() && node()->hasTagName(iframeTag) && toHTMLIFrameElement(node())->shouldDisplaySeamlessly();
 }
 
 bool RenderIFrame::requiresLayer() const
 {
     return RenderPart::requiresLayer() || style()->resize() != RESIZE_NONE;
 }
 
 RenderView* RenderIFrame::contentRootRenderer() const
 {
     // FIXME: Is this always a valid cast? What about plugins?
@@ skipping 42 matching lines @@
     }
 
     m_overflow.clear();
     addVisualEffectOverflow();
     updateLayerTransform();
 
     setNeedsLayout(false);
 }
 
 }