popover menubar focus handling is broken
GtkPopoverMenuBar had pretty well-working focus handling (similar to GtkMenuBar) when I merged it. It got broken by
commit 4eb07797 Author: Benjamin Otte otte@redhat.com Date: Tue Oct 15 16:30:46 2019 +0200
widget: Don't grab focus when can-focus == false
... inside the default vfunc.
Instead, walk the children until we find the first widget that can be
focused. If no child can be focused, return FALSE from grab_focus.