Use isSVG*Element() helpers more in SVG code (Part 3)

Source/core/rendering/svg/RenderSVGResourceMasker.cpp

 /*
  * Copyright (C) Research In Motion Limited 2009-2010. 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 135 matching lines @@
             continue;
 
         SVGRenderingContext::renderSubtree(context, renderer, contentTransform);
     }
 
     return context->endRecording();
 }
 
 void RenderSVGResourceMasker::calculateMaskContentRepaintRect()
 {
-    for (Element* childElement = ElementTraversal::firstWithin(*element()); childElement; childElement = ElementTraversal::nextSibling(*childElement)) {
+    for (SVGElement* childElement = Traversal<SVGElement>::firstChild(*element()); childElement; childElement = Traversal<SVGElement>::nextSibling(*childElement)) {
         RenderObject* renderer = childElement->renderer();
-        if (!childElement->isSVGElement() || !renderer)
+        if (!renderer)
             continue;
         RenderStyle* style = renderer->style();
         if (!style || style->display() == NONE || style->visibility() != VISIBLE)
              continue;
         m_maskContentBoundaries.unite(renderer->localToParentTransform().mapRect(renderer->repaintRectInLocalCoordinates()));
     }
 }
 
 FloatRect RenderSVGResourceMasker::resourceBoundingBox(const RenderObject* object)
 {
@@ skipping 16 matching lines @@
         transform.translate(objectBoundingBox.x(), objectBoundingBox.y());
         transform.scaleNonUniform(objectBoundingBox.width(), objectBoundingBox.height());
         maskRect = transform.mapRect(maskRect);
     }
 
     maskRect.intersect(maskBoundaries);
     return maskRect;
 }
 
 }