Make CSSStyleDeclaration getter/setter custom

Source/core/css/CSSStyleDeclaration.idl

 /*
  * Copyright (C) 2006, 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Samuel Weinig <sam.weinig@gmail.com>
  *
  * 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.
  *
  * This library is distributed in the hope that it will be useful,
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     [TreatReturnedNullStringAs=Null] DOMString          getPropertyValue([Default=Undefined] optional DOMString propertyName);
     CSSValue           getPropertyCSSValue([Default=Undefined] optional DOMString propertyName);
     [TreatReturnedNullStringAs=Null, RaisesException] DOMString          removeProperty([Default=Undefined] optional DOMString propertyName);
     [TreatReturnedNullStringAs=Null] DOMString          getPropertyPriority([Default=Undefined] optional DOMString propertyName);
      [RaisesException] void setProperty([Default=Undefined] optional DOMString propertyName, 
                                     [TreatNullAs=NullString,Default=Undefined] optional DOMString value, 
                                     [Default=Undefined] optional DOMString priority);
 
     readonly attribute unsigned long    length;
     getter DOMString          item([Default=Undefined] optional unsigned long index);
-    [ImplementedAs=anonymousNamedGetter, TreatReturnedNullStringAs=Null] getter (DOMString or float) (DOMString name);
-    [ImplementedAs=anonymousNamedSetter, RaisesException] setter void (DOMString propertyName, [TreatNullAs=NullString] DOMString propertyValue);
+    [Custom] getter (DOMString or float) (DOMString name);
+    [Custom] setter void (DOMString propertyName, [TreatNullAs=NullString] DOMString propertyValue);
     readonly attribute CSSRule          parentRule;
 };