Remove TreatNullAs=NullString for CSS*Rule

Source/core/css/CSSKeyframesRule.idl

Index: Source/core/css/CSSKeyframesRule.idl
diff --git a/Source/core/css/CSSKeyframesRule.idl b/Source/core/css/CSSKeyframesRule.idl
index c94dbc47e9b29e588a0ceee6e1b0dfd9a26ee83b..d97dd4aae3bc3b97f9390ed7e2bcccce0adb3a1d 100644
--- a/Source/core/css/CSSKeyframesRule.idl
+++ b/Source/core/css/CSSKeyframesRule.idl
@@ -28,8 +28,7 @@
 
 // Introduced in DOM Level ?:
 interface CSSKeyframesRule : CSSRule {
-
-    [TreatReturnedNullStringAs=Null, TreatNullAs=NullString] attribute DOMString name;
+    attribute DOMString name;
     readonly attribute CSSRuleList cssRules;
 
     [ImplementedAs=item, NotEnumerable] getter CSSKeyframeRule(unsigned long index);
@@ -37,4 +36,3 @@ interface CSSKeyframesRule : CSSRule {
     void deleteRule([Default=Undefined] optional DOMString key);
     CSSKeyframeRule findRule([Default=Undefined] optional DOMString key);
 };
-