Make MediaList API arguments mandatory

Source/core/css/MediaList.idl

Index: Source/core/css/MediaList.idl
diff --git a/Source/core/css/MediaList.idl b/Source/core/css/MediaList.idl
index 9d2661732a1c2cbc8fce31a48dcff42da407c5e4..20ef3ec883560a23d138b8c7f351203a8c320300 100644
--- a/Source/core/css/MediaList.idl
+++ b/Source/core/css/MediaList.idl
@@ -30,9 +30,9 @@
     [TreatNullAs=NullString, TreatReturnedNullStringAs=Null] attribute DOMString mediaText;
     readonly attribute unsigned long length;
 
-    [TreatReturnedNullStringAs=Null] getter DOMString item([Default=Undefined] optional unsigned long index);
-    [RaisesException] void deleteMedium([Default=Undefined] optional DOMString oldMedium);
-    [RaisesException] void appendMedium([Default=Undefined] optional DOMString newMedium);
+    [TreatReturnedNullStringAs=Null] getter DOMString item(unsigned long index);
+    [RaisesException] void deleteMedium(DOMString oldMedium);
+    [RaisesException] void appendMedium(DOMString newMedium);
 
 };