Introduce toSVGRadialGradientElement(), and use it

Source/core/svg/SVGRadialGradientElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007 Rob Buis <buis@kde.org>
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008 Dirk Schulze <krit@webkit.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
@@ skipping 141 matching lines @@
             attributes.setGradientTransform(transform);
         }
 
         if (!attributes.hasStops()) {
             const Vector<Gradient::ColorStop>& stops(current->buildStops());
             if (!stops.isEmpty())
                 attributes.setStops(stops);
         }
 
         if (isRadial) {
-            SVGRadialGradientElement* radial = static_cast<SVGRadialGradientElement*>(current);
+            SVGRadialGradientElement* radial = toSVGRadialGradientElement(current);
 
             if (!attributes.hasCx() && current->hasAttribute(SVGNames::cxAttr))
                 attributes.setCx(radial->cxCurrentValue());
 
             if (!attributes.hasCy() && current->hasAttribute(SVGNames::cyAttr))
                 attributes.setCy(radial->cyCurrentValue());
 
             if (!attributes.hasR() && current->hasAttribute(SVGNames::rAttr))
                 attributes.setR(radial->rCurrentValue());
 
@@ skipping 38 matching lines @@
 {
     return cxCurrentValue().isRelative()
         || cyCurrentValue().isRelative()
         || rCurrentValue().isRelative()
         || fxCurrentValue().isRelative()
         || fyCurrentValue().isRelative()
         || frCurrentValue().isRelative();
 }
 
 }