It's possible in some corner cases for the status of the topwindow
to change and make it not fullscreen without ::restacked being
changed. One way that it could happen with the old code was if the
layer of the top window changed from NORMAL to FULLSCREEN.
Change the logic not to look at the layer, which is a function of
Mutter's *intended* stacking, rather than the *actual* stacking,
which is what ::restacked gives you. Instead, look at the top
portion of the stack, down to the first non-override-redirect
window, and see if their are any monitor-sized windows there.
Connect to changes on the top portion of the stack, so we know
if conditions change.
https://bugzilla.gnome.org/show_bug.cgi?id=649748
6119b44746