Add toRenderSVGResourceRadialGradient() fuction, and use it.

Source/core/rendering/svg/SVGRenderTreeAsText.cpp

 /*
  * Copyright (C) 2004, 2005, 2007, 2009 Apple Inc. All rights reserved.
  *           (C) 2005 Rob Buis <buis@kde.org>
  *           (C) 2006 Alexander Kellett <lypanov@kde.org>
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
@@ skipping 523 matching lines @@
         RenderSVGResourceLinearGradient* gradient = static_cast<RenderSVGResourceLinearGradient*>(resource);
 
         // Dump final results that are used for rendering. No use in asking SVGGradientElement for its gradientUnits(), as it may
         // link to other gradients using xlink:href, we need to build the full inheritance chain, aka. collectGradientProperties()
         LinearGradientAttributes attributes;
         toSVGLinearGradientElement(gradient->element())->collectGradientAttributes(attributes);
         writeCommonGradientProperties(ts, attributes.spreadMethod(), attributes.gradientTransform(), attributes.gradientUnits());
 
         ts << " [start=" << gradient->startPoint(attributes) << "] [end=" << gradient->endPoint(attributes) << "]\n";
     }  else if (resource->resourceType() == RadialGradientResourceType) {
-        RenderSVGResourceRadialGradient* gradient = static_cast<RenderSVGResourceRadialGradient*>(resource);
+        RenderSVGResourceRadialGradient* gradient = toRenderSVGResourceRadialGradient(resource);
 
         // Dump final results that are used for rendering. No use in asking SVGGradientElement for its gradientUnits(), as it may
         // link to other gradients using xlink:href, we need to build the full inheritance chain, aka. collectGradientProperties()
         RadialGradientAttributes attributes;
         toSVGRadialGradientElement(gradient->element())->collectGradientAttributes(attributes);
         writeCommonGradientProperties(ts, attributes.spreadMethod(), attributes.gradientTransform(), attributes.gradientUnits());
 
         FloatPoint focalPoint = gradient->focalPoint(attributes);
         FloatPoint centerPoint = gradient->centerPoint(attributes);
         float radius = gradient->radius(attributes);
@@ skipping 104 matching lines @@
             ts << " ";
             writeNameAndQuotedValue(ts, "filter", svgStyle->filterResource());
             ts << " ";
             writeStandardPrefix(ts, *filter, 0);
             ts << " " << filter->resourceBoundingBox(&renderer) << "\n";
         }
     }
 }
 
 } // namespace WebCore