disable alt key toggling the menu bar
Following the discussion at https://trac.torproject.org/projects/tor/ticket/31512#comment:10 where I suspect changes to the inner window are happening. Of the plethora of things that can alter the inner window measurements....
ui.key.menuAccessKey
= 0
will disable the alt key toggling the menu bar on and off
Letterboxing solves this issue, but it can also be very annoying if your letterboxed height keeps jumping sizes. It's not the only thing that can alter your height, but it is something that users can inadvertently trigger (I have fat thumbs, 10 of them, and it really annoys me: hence I set this myself in Firefox)
I'll leave it up to you. If the threat is mitigated, then why remove functionality. Feel free to close... or action ...