Comment 2 for bug 609326

> Tabs in the staff client are missing the tab close icon with new
> xulrunner, only option is to use ctrl+w to close tab.

Or File->Close Tab from the top-level menu.

Yeah, I'm not sure what sort of debate has been happening in the
Mozilla community with this, but from what I understood a long time
ago, most of the functional enhancements for tabbox/tabbrowser were
Firefox specific, and did not make sense outside of that context. So
it's a probably a sort of throw the baby out with the bathwater
scenario, where xulrunner gets stocked with a minimal tab browser, and
Firefox does their own thing.

We can could take some of the code from the older xulrunner:

<hbox class="tabs-closebutton-box" align="center" pack="end">
<toolbarbutton ondblclick="event.stopPropagation();"
class="tabs-closebutton close-button"
xbl:inherits="disabled=disableclose,oncommand=onclosetab"
xmlns:xbl="http://www.mozilla.org/xbl"
oncommand="g.menu.close_tab()"/>
</hbox>

But just shoving that in menu_frame_overlay.xul:<tabs></tabs> is kind
of brittle (especially if we try to put it next some of the anonymous
nodes that XBL uses to construct the element--such things are prone to
changing as we've seen), and we'd also need to disable it whenever we
were down to just one tab.

We could roll our own implementation of tabbox, but I don't think it's
worth it. May be better to wade into the Mozilla community and see
what's up.

-- Jason