We introduced the absolute_origin_changed flag when preparing for the
removal of ClutterAllocationFlags in commit dc8e5c7f8b. Turns out in the
mean-time commit df4eeff6f2 happened, which renders the whole
absolute_origin_changed flag moot.
That's because we now notify the whole subtree about the absolute origin
change by calling transform_changed() when the allocation of an actor
changes. transform_changed() traverses the subtree and calls
absolute_geometry_changed() on every actor immediately, which renders
the whole propagation of the absolute_origin_changed flag obsolete.
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1498
76578e5aa0