Introduce toSVGMaskElement(), and use it

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 73 matching lines @@
         m_masker.set(object, new MaskerData);
 
     MaskerData* maskerData = m_masker.get(object);
 
     AffineTransform absoluteTransform;
     SVGRenderingContext::calculateTransformationToOutermostCoordinateSystem(object, absoluteTransform);
 
     FloatRect repaintRect = object->repaintRectInLocalCoordinates();
 
     if (!maskerData->maskImage && !repaintRect.isEmpty()) {
-        SVGMaskElement* maskElement = static_cast<SVGMaskElement*>(node());
+        SVGMaskElement* maskElement = toSVGMaskElement(node());
         if (!maskElement)
             return false;
 
         ASSERT(style());
         const SVGRenderStyle* svgStyle = style()->svgStyle();
         ASSERT(svgStyle);
         ColorSpace colorSpace = svgStyle->colorInterpolation() == CI_LINEARRGB ? ColorSpaceLinearRGB : ColorSpaceDeviceRGB;
         if (!SVGRenderingContext::createImageBuffer(repaintRect, absoluteTransform, maskerData->maskImage, Unaccelerated))
             return false;
 
@@ skipping 55 matching lines @@
             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(RenderObject* object)
 {
-    SVGMaskElement* maskElement = static_cast<SVGMaskElement*>(node());
+    SVGMaskElement* maskElement = toSVGMaskElement(node());
     ASSERT(maskElement);
 
     FloatRect objectBoundingBox = object->objectBoundingBox();
     FloatRect maskBoundaries = SVGLengthContext::resolveRectangle<SVGMaskElement>(maskElement, maskElement->maskUnitsCurrentValue(), objectBoundingBox);
 
     // Resource was not layouted yet. Give back clipping rect of the mask.
     if (selfNeedsLayout())
         return maskBoundaries;
 
     if (m_maskContentBoundaries.isEmpty())
         calculateMaskContentRepaintRect();
 
     FloatRect maskRect = m_maskContentBoundaries;
     if (maskElement->maskContentUnitsCurrentValue() == SVGUnitTypes::SVG_UNIT_TYPE_OBJECTBOUNDINGBOX) {
         AffineTransform transform;
         transform.translate(objectBoundingBox.x(), objectBoundingBox.y());
         transform.scaleNonUniform(objectBoundingBox.width(), objectBoundingBox.height());
         maskRect = transform.mapRect(maskRect);
     }
 
     maskRect.intersect(maskBoundaries);
     return maskRect;
 }
 
 }