After 4faeb12731, the maximum time allowed for an update to happen
is calculated as:
max_render_time_allowed = refresh_interval - 1000 * sync_delay;
However, extremely small refresh intervals -- that come as consequence
to extremely high refresh rates -- may fall into an odd numerical range
when refresh_interval < 1000 * sync_delay. That would give us a negative
time.
To be extra cautious about it, add another sanity check for this case.
Change suggested by Jasper St. Pierre.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/363
1dbf25afa1