Make CSSKeyframesRule function arguments non-optional

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 9176870da40f3ed19e4879264bb387cf39744aea..f67ea68d6d557d8900ae635f2fb9623142fdc7d4 100644
--- a/Source/core/css/CSSKeyframesRule.idl
+++ b/Source/core/css/CSSKeyframesRule.idl
@@ -32,8 +32,8 @@ interface CSSKeyframesRule : CSSRule {
     readonly attribute CSSRuleList cssRules;
 
     [ImplementedAs=item, NotEnumerable] getter CSSKeyframeRule (unsigned long index);
-    [MeasureAs=CSSKeyframesRuleInsertRule] void insertRule([Default=Undefined] optional DOMString rule);
-    [ImplementedAs=insertRule, MeasureAs=CSSKeyframesRuleAppendRule] void appendRule([Default=Undefined] optional DOMString rule);
-    void deleteRule([Default=Undefined] optional DOMString key);
-    CSSKeyframeRule findRule([Default=Undefined] optional DOMString key);
+    [MeasureAs=CSSKeyframesRuleInsertRule] void insertRule(DOMString rule);
+    [ImplementedAs=insertRule, MeasureAs=CSSKeyframesRuleAppendRule] void appendRule(DOMString rule);
+    void deleteRule(DOMString key);
+    CSSKeyframeRule? findRule(DOMString key);
 };