How to find the different controls on a FireFox Browser. ?

So the original question is to be able to find different controls on a
XUL application. But to make it simpler, i want to be able to find
various controls present on the Firefox browser through my JavaScript.
I am trying to use the interfaces being exposed by XULRunner. The
thing i have tried thus far.

function findXULWindow(txt)
{
        var wm = Components.classes["@mozilla.org/appshell/window-
mediator;1"]
                   .getService(Components.interfaces.nsIWindowMediator);

        var enumerator = wm.getEnumerator("navigator:browser");
        alert("1");
        while(enumerator.hasMoreElements()) {
                var win = enumerator.getNext();

                alert("2");



               }

}

This code when i run on a Firefox is part of extension to FF  , gives
me the reference of the top level xul window which in my case is the
browser and the loop runs once for one open browser instance.

What i am typically interested is in enumerating the different
controls( forward \backward buttons, menus..etc ) available on the
FireFox Browser.  Any pointers \help is much appreciated.