I use the Firefox Nightly build for my daily use, and it works fine, except for one little annoyance: the Menu Bar doesn't merge with the taskbar like it does in every single application in Ubuntu. (well, excepting those started by gksu, of course.)

If my problem doesn't quite make sense, here's a screenshot:

see how the options File, Edit, View, etc., are not beautifully merged with the taskbar like they should be? Does anybody have any ideas on how to fix this?
My suspicion is that I lost the add-on that is supposed to do that, but I'm not quite sure whether that's the problem, or where to find the .xpi file. At askubuntu.com, somebody had accidentally lost his Global Menu Bar Integration add-on, but the only answer that had what I needed contained a dead link. I asked about my problem, but my question was too specific, and was locked. I now turn to you, the Ubuntu Forums, to see what you can do.