DEFINE_CSS_VALUE_TYPE_CASTS starts to use DEFINE_TYPE_CASTS

Source/core/css/CSSVariableValue.h

 /*
  * Copyright (C) 2012 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 41 matching lines @@
         : CSSValue(VariableClass)
         , m_name(name)
         , m_value(value)
     {
     }
 
     const AtomicString m_name;
     const String m_value;
 };
 
-DEFINE_CSS_VALUE_TYPE_CASTS(VariableValue);
+DEFINE_CSS_VALUE_TYPE_CASTS(CSSVariableValue, isVariableValue());
 
 }
 
 #endif /* CSSVariableValue_h */