Flip flop resize, which is the result of respecting ConfigureNotify
makes test annoyingly racy, as one cannot do
clutter_actor_set_size (stage, 1024, 768);
wait_for_paint (stage);
g_assert_assert (clutter_actor_get_width (stage) == 1024);
The reason for this is any lingering ConfigureNotify event that might
arrive in an inconvenient time in response to some earlier resize.
In order to not risk breaking any current behavior in the X11 CM case
(running as a compositing window manager), only avoid changing the stage
size in response to ConfigureNotify when running nested.
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1404
c6fc3a8953