Add toSVGClipPathElement(), and use it

Source/core/svg/SVGSVGElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010 Rob Buis <buis@kde.org>
  * Copyright (C) 2007 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 700 matching lines @@
     }
 
     // Spec: If the SVG fragment identifier addresses a ‘view’ element within an SVG document (e.g., MyDrawing.svg#MyView
     // or MyDrawing.svg#xpointer(id('MyView'))) then the closest ancestor ‘svg’ element is displayed in the viewport.
     // Any view specification attributes included on the given ‘view’ element override the corresponding view specification
     // attributes on the closest ancestor ‘svg’ element.
     if (anchorNode && anchorNode->hasTagName(SVGNames::viewTag)) {
         if (SVGViewElement* viewElement = anchorNode->hasTagName(SVGNames::viewTag) ? static_cast<SVGViewElement*>(anchorNode) : 0) {
             SVGElement* element = SVGLocatable::nearestViewportElement(viewElement);
             if (element->hasTagName(SVGNames::svgTag)) {
-                SVGSVGElement* svg = static_cast<SVGSVGElement*>(element);
+                SVGSVGElement* svg = toSVGSVGElement(element);
                 svg->inheritViewAttributes(viewElement);
 
                 if (RenderObject* renderer = svg->renderer())
                     RenderSVGResource::markForLayoutAndParentResourceInvalidation(renderer);
             }
         }
         return;
     }
 
     // FIXME: We need to decide which <svg> to focus on, and zoom to it.
@@ skipping 36 matching lines @@
             continue;
 
         Element* element = toElement(node);
         if (element->getIdAttribute() == id)
             return element;
     }
     return 0;
 }
 
 }