I was wondering why tokens submitted by a GTK3 based launchee would always have a 0 serial on a touch based device (and would thus be rejected by the compositor).
Since the touch data is released on touch up
_gdk_wayland_seat_get_last_implicit_grab_serial will return 0 serial
most of the time for touch only devices. This breaks xdg activation as
the compositor will reject tokens that have a 0 serial set via
Avoid that by tracking touch serials on the seat itself too.
We only use that if no other touch serial was picked to make sure we dont break the sequence <-> serial relation.
This unbreaks the phosh's splash screen timing out on recent GTK3.