Expose CSSGroupingRule

Source/core/css/CSSMediaRule.idl

Index: Source/core/css/CSSMediaRule.idl
diff --git a/Source/core/css/CSSMediaRule.idl b/Source/core/css/CSSMediaRule.idl
index e7376fe86d737d8b3446877040756bfab1649892..1e6c85aecc27a9d90adda207b7df699903ad008d 100644
--- a/Source/core/css/CSSMediaRule.idl
+++ b/Source/core/css/CSSMediaRule.idl
@@ -20,14 +20,7 @@
 
 // http://dev.w3.org/csswg/cssom/#the-cssmediarule-interface
 
-interface CSSMediaRule : CSSRule {
+interface CSSMediaRule : CSSGroupingRule {
     // TODO(philipj): media should have [PutForwards=mediaText].
     [SameObject] readonly attribute MediaList media;
-
-    // TODO(philipj): Implement CSSGroupingRule and inherit from it.
-    // crbug.com/496381
-    // http://dev.w3.org/csswg/cssom/#the-cssgroupingrule-interface
-    [SameObject] readonly attribute CSSRuleList cssRules;
-    [RaisesException] unsigned long insertRule(DOMString rule, unsigned long index);
-    [RaisesException] void deleteRule(unsigned long index);
 };