select.add() should support optgroup adding and before index

Source/core/html/HTMLSelectElement.idl

Index: Source/core/html/HTMLSelectElement.idl
diff --git a/Source/core/html/HTMLSelectElement.idl b/Source/core/html/HTMLSelectElement.idl
index 658e9918f3f82d8a1495b94dc29a9776ae1f5941..abd95e9d1e287b2d100190e0310751de4b89cd45 100644
--- a/Source/core/html/HTMLSelectElement.idl
+++ b/Source/core/html/HTMLSelectElement.idl
@@ -36,8 +36,9 @@ interface HTMLSelectElement : HTMLElement {
     getter Element item(unsigned long index);
     [RaisesException, StrictTypeChecking] setter HTMLOptionElement (unsigned long index, HTMLOptionElement? value);
     Element namedItem([Default=Undefined] optional DOMString name);
-    [RaisesException] void add([Default=Undefined] optional HTMLElement element,
-                               [Default=Undefined] optional HTMLElement before);
+    [RaisesException] void add(HTMLElement element,
+                               [Default=Undefined] optional HTMLElement? before);
+    [RaisesException, ImplementedAs=addBeforeOptionAtIndex] void add(HTMLElement element, long before);
     void remove(long index);
     [RaisesException] void remove();
     readonly attribute HTMLCollection selectedOptions;