Make CSSKeyframesRule.insertRule an alias of appendRule

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 28835321159cf8ca7390edc866f7772259f24132..c138ab03e43aa5eaae0fbf195116cb7b0c8a9a55 100644
--- a/Source/core/css/CSSKeyframesRule.idl
+++ b/Source/core/css/CSSKeyframesRule.idl
@@ -32,11 +32,11 @@ interface CSSKeyframesRule : CSSRule {
     attribute DOMString name;
     readonly attribute CSSRuleList cssRules;
 
-    [ImplementedAs=insertRule, MeasureAs=CSSKeyframesRuleAppendRule] void appendRule(DOMString rule);
+    [MeasureAs=CSSKeyframesRuleAppendRule] void appendRule(DOMString rule);
     void deleteRule(DOMString select);
     CSSKeyframeRule? findRule(DOMString select);
 
     // Non-standard APIs
     [ImplementedAs=item, NotEnumerable] getter CSSKeyframeRule (unsigned long index);
-    [DeprecateAs=CSSKeyframesRuleInsertRule] void insertRule(DOMString rule);
+    [DeprecateAs=CSSKeyframesRuleInsertRule, ImplementedAs=appendRule] void insertRule(DOMString rule);
 };