Add toRenderSVGResourceFilter() 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 474 matching lines @@
 
     RenderSVGResourceContainer* resource = const_cast<RenderObject&>(object).toRenderSVGResourceContainer();
     ASSERT(resource);
 
     if (resource->resourceType() == MaskerResourceType) {
         RenderSVGResourceMasker* masker = toRenderSVGResourceMasker(resource);
         writeNameValuePair(ts, "maskUnits", masker->maskUnits());
         writeNameValuePair(ts, "maskContentUnits", masker->maskContentUnits());
         ts << "\n";
     } else if (resource->resourceType() == FilterResourceType) {
-        RenderSVGResourceFilter* filter = static_cast<RenderSVGResourceFilter*>(resource);
+        RenderSVGResourceFilter* filter = toRenderSVGResourceFilter(resource);
         writeNameValuePair(ts, "filterUnits", filter->filterUnits());
         writeNameValuePair(ts, "primitiveUnits", filter->primitiveUnits());
         ts << "\n";
         // Creating a placeholder filter which is passed to the builder.
         FloatRect dummyRect;
         RefPtr<SVGFilter> dummyFilter = SVGFilter::create(AffineTransform(), dummyRect, dummyRect, dummyRect, true);
         if (RefPtr<SVGFilterBuilder> builder = filter->buildPrimitives(dummyFilter.get())) {
             if (FilterEffect* lastEffect = builder->lastEffect())
                 lastEffect->externalRepresentation(ts, indent + 1);
         }
@@ skipping 153 matching lines @@
             ts << " ";
             writeNameAndQuotedValue(ts, "filter", svgStyle->filterResource());
             ts << " ";
             writeStandardPrefix(ts, *filter, 0);
             ts << " " << filter->resourceBoundingBox(&renderer) << "\n";
         }
     }
 }
 
 } // namespace WebCore