An attempt to follow-through on !1877 (closed), taking review comments into account.
Original commits are untouched, I only tried to move the functionality into its own separate class.
Arch Linux VM using virtio-gpu/virgl 1. gnome-shell --wayland 2. Start firefox with MOZ_ENABLE_WAYLAND=1 3. Un-maximize firefox, move window around (had a debug print showing new code being hit) and went into/out of the overview