Use DEFINE_CSS_VALUE_TYPE_CASTS instead of using manual type cast function for CSSShaderValue

Source/core/css/CSSShaderValue.h

 /*
  * Copyright (C) 2011 Adobe Systems Incorporated. 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 notice, this list of conditions and the following
  *    disclaimer.
@@ skipping 46 matching lines @@
 
 private:
     CSSShaderValue(const String& url);
 
     String m_url;
     String m_format;
     RefPtr<StyleShader> m_shader;
     bool m_accessedShader;
 };
 
-// This will catch anyone doing an unnecessary cast.
-CSSShaderValue* toCSSShaderValue(const CSSShaderValue*);
-
-inline CSSShaderValue* toCSSShaderValue(CSSValue* value)
-{
-    return value->isCSSShaderValue() ? static_cast<CSSShaderValue*>(value) : 0;
-}
+DEFINE_CSS_VALUE_TYPE_CASTS(ShaderValue);
 
 } // namespace WebCore
 
 
 #endif // CSSShaderValue_h