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

Source/core/svg/SVGPaint.h

 /*
  * Copyright (C) 2004, 2005 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007 Rob Buis <buis@kde.org>
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmial.com>
  * Copyright (C) Research In Motion Limited 2011. 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.
@@ skipping 98 matching lines @@
     }
 
 private:
     SVGPaint(const SVGPaintType&, const String& uri = String());
     SVGPaint(const SVGPaint& cloneFrom);
 
     SVGPaintType m_paintType;
     String m_uri;
 };
 
+// This will catch anyone doing an unnecessary cast.
+SVGPaint* toSVGPaint(const SVGColor*);
+
+inline SVGPaint* toSVGPaint(CSSValue* value)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!value || value->isSVGPaint());
+    return static_cast<SVGPaint*>(value);
+}
+
+inline const SVGPaint* toSVGPaint(const CSSValue* value)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!value || value->isSVGPaint());
+    return static_cast<const SVGPaint*>(value);
+}
+
 } // namespace WebCore
 
 #endif // SVGPaint_h