I'm not entirely sure how to reproduce this. I basically selected every option the toolbar has available and then closed the tab. There are scads of them, though. I think it was something in the right third of the toolbar or so, though. I can reproduce this in version 1.1.9 and 1.2 Developer CCd and notified via AMO.
This is the 18th most popular add-on on AMO with over 1 million users, so it might be worth ranking higher than MemShrink:P3. It'd be nice to know if it still occurs in FF15, which has bug 695480's patch.
(In reply to Nicholas Nethercote [:njn] from comment #1) > This is the 18th most popular add-on on AMO with over 1 million users, so it > might be worth ranking higher than MemShrink:P3. Turns out it's hard to trigger, so P3 seems ok.
Misc > Display Ruler seems to be one way to trigger this. There seems to be some major bugginess with the Misc menu in general, though. Multiple times I wound up with ‘Display Line Guides’ checked with no way to disable it (even when I hadn't clicked it to begin with).
I found and fixed the zombie compartments being created by the 'Display Ruler' feature and it will be part of the next version I submit for review. I'll update once the new version is reviewed and given the all clear. In the meantime if anyone finds any other features that cause zombie compartments please update this ticket as I have not discovered any yet.
Seems fixed in version 1.2.1. The bugginess mentioned in comment 3 remains.