GtkEntryCompletion dropdown not shown on secondary display under wayland
Steps to reproduce
On a two screen wayland session, open gtk3-demo/entry/entry-completion example on the secondary screen (the one without gnome-shell top bar). Type 'to'. A dropdown should appear with the completion suggestions, but nothing happens. It work just fine on the primary screen, or both screens under X11.
This is on an up to date fedora 28 install (gtk3 3.22.30).
This impacts geary contact entry, and epiphany url entry.