Use isSVG*Element() helpers more in SVG code (Part 2)

Source/core/svg/SVGPatternElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007 Rob Buis <buis@kde.org>
  * 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.
  *
@@ skipping 174 matching lines @@
 {
     HashSet<const SVGPatternElement*> processedPatterns;
     const SVGPatternElement* current = this;
 
     while (true) {
         setPatternAttributes(current, attributes);
         processedPatterns.add(current);
 
         // Respect xlink:href, take attributes from referenced element
         Node* refNode = SVGURIReference::targetElementFromIRIString(current->hrefString(), document());
-        if (refNode && refNode->hasTagName(SVGNames::patternTag)) {
-            current = toSVGPatternElement(const_cast<const Node*>(refNode));
+        if (isSVGPatternElement(refNode)) {
+            current = toSVGPatternElement(refNode);
 
             // Cycle detection
             if (processedPatterns.contains(current))
                 return;
         } else {
             return;
         }
     }
 
     ASSERT_NOT_REACHED();
 }
 
 AffineTransform SVGPatternElement::localCoordinateSpaceTransform(SVGElement::CTMScope) const
 {
     AffineTransform matrix;
     m_patternTransform->currentValue()->concatenate(matrix);
     return matrix;
 }
 
 bool SVGPatternElement::selfHasRelativeLengths() const
 {
     return m_x->currentValue()->isRelative()
         || m_y->currentValue()->isRelative()
         || m_width->currentValue()->isRelative()
         || m_height->currentValue()->isRelative();
 }
 
 }