Comment 64 for bug 1987976

Seems possible, but I don't know what might be going on in the reporter's machine, since that's a setup that works ~everywhere else?

To double-check, can you confirm that `MOZ_GTK_TITLEBAR_DECORATION=system` works, but `MOZ_GTK_TITLEBAR_DECORATION=client` doesn't? Also does enabling the system titlebar (from the customize page) prevent it from happening?