IDL: make optional arguments (without default) explicit sometimes

Source/core/plugins/PluginArray.idl

Index: Source/core/plugins/PluginArray.idl
diff --git a/Source/core/plugins/PluginArray.idl b/Source/core/plugins/PluginArray.idl
index dc2ab1d31a45fcde0b9fb6d1c82107233de56889..c481909873fd022f231fc28b882980d149a3811b 100644
--- a/Source/core/plugins/PluginArray.idl
+++ b/Source/core/plugins/PluginArray.idl
@@ -23,9 +23,9 @@
     ImplementedAs=DOMPluginArray
 ] interface PluginArray {
     readonly attribute unsigned long length;
-    getter Plugin item([Default=Undefined] optional unsigned long index);
-    Plugin namedItem([Default=Undefined] optional DOMString name);
-    [NotEnumerable, ImplementedAs=namedItem] getter Plugin ([Default=Undefined] optional DOMString name);
-    void refresh([Default=Undefined] optional boolean reload);
+    getter Plugin item(optional unsigned long index);
+    Plugin namedItem(optional DOMString name);
+    [NotEnumerable, ImplementedAs=namedItem] getter Plugin (optional DOMString name);
+    void refresh(optional boolean reload);
 };