Make CSSStyleDeclaration getter/setter custom

Source/core/css/CSSStyleDeclaration.idl

Index: Source/core/css/CSSStyleDeclaration.idl
diff --git a/Source/core/css/CSSStyleDeclaration.idl b/Source/core/css/CSSStyleDeclaration.idl
index 2d965962031fcad273d1057cadf5c6d8ba78fbf2..103e0c41a27cee8697d6ca0d9b22f4ce34487b6a 100644
--- a/Source/core/css/CSSStyleDeclaration.idl
+++ b/Source/core/css/CSSStyleDeclaration.idl
@@ -35,8 +35,8 @@
 
     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;
 };