Add toSVGColor|Paint() to cleanup static_cast<>, and use it

Source/bindings/v8/custom/V8CSSValueCustom.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 38 matching lines @@
         return wrap(toCSSTransformValue(impl), creationContext, isolate);
     if (impl->isMixFunctionValue())
         return wrap(toCSSMixFunctionValue(impl), creationContext, isolate);
     if (impl->isFilterValue())
         return wrap(toCSSFilterValue(impl), creationContext, isolate);
     if (impl->isValueList())
         return wrap(toCSSValueList(impl), creationContext, isolate);
     if (impl->isPrimitiveValue())
         return wrap(toCSSPrimitiveValue(impl), creationContext, isolate);
     if (impl->isSVGPaint())
-        return wrap(static_cast<SVGPaint*>(impl), creationContext, isolate);
+        return wrap(toSVGPaint(impl), creationContext, isolate);
     if (impl->isSVGColor())
-        return wrap(static_cast<SVGColor*>(impl), creationContext, isolate);
+        return wrap(toSVGColor(impl), creationContext, isolate);
     return V8CSSValue::createWrapper(impl, creationContext, isolate);
 }
 
 } // namespace WebCore