Currently, we will notify the display about a new window being created
during the constructed phase of the GObject. During this time,
property-change notifications are frozen by GObject, so we'll emit a few
::notify signals only after the window-created signal, although
the actual property change happened before that.
This caused confusion in gnome-shell code where a notify::skip-taskbar =
true emission was seen when the property already was true inside a
window-created handler before.
In order to fix that that, we notify the window creation
post-construction
of the GObject on GInitable.init vfunc
Details
https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/6119#note_1598983
Fixes https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/6119
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2703>