Use toSVGFilterElement instead of static_cast<..>

Source/core/rendering/svg/SVGResources.cpp

 /*
  * Copyright (C) Research In Motion Limited 2010. 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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 129 matching lines @@
 }
 
 static inline String targetReferenceFromResource(SVGElement* element)
 {
     String target;
     if (element->hasTagName(SVGNames::patternTag))
         target = static_cast<SVGPatternElement*>(element)->hrefCurrentValue();
     else if (element->hasTagName(SVGNames::linearGradientTag) || element->hasTagName(SVGNames::radialGradientTag))
         target = static_cast<SVGGradientElement*>(element)->hrefCurrentValue();
     else if (element->hasTagName(SVGNames::filterTag))
-        target = static_cast<SVGFilterElement*>(element)->hrefCurrentValue();
+        target = toSVGFilterElement(element)->hrefCurrentValue();
     else
         ASSERT_NOT_REACHED();
 
     return SVGURIReference::fragmentIdentifierFromIRIString(target, element->document());
 }
 
 static inline RenderSVGResourceContainer* paintingResourceFromSVGPaint(Document* document, const SVGPaint::SVGPaintType& paintType, const String& paintUri, AtomicString& id, bool& hasPendingResource)
 {
     if (paintType != SVGPaint::SVG_PAINTTYPE_URI && paintType != SVGPaint::SVG_PAINTTYPE_URI_RGBCOLOR)
         return 0;
@@ skipping 495 matching lines @@
         if (RenderSVGResourceContainer* stroke = m_fillStrokeData->stroke)
             fprintf(stderr, " |-> Stroke     : %p (node=%p)\n", stroke, stroke->node());
     }
 
     if (m_linkedResource)
         fprintf(stderr, " |-> xlink:href : %p (node=%p)\n", m_linkedResource, m_linkedResource->node());
 }
 #endif
 
 }