wayland: do not explicitly focus xdg_popup

The keyboard focus semantics for non-grabbing xdg_shell v6 popups is
pretty undefined.

Same applies for subsurfaces, but in practice, subsurfaces never receive
keyboard focus, so it makes sense to do the same for non-grabbing
popups.

https://bugzilla.gnome.org/show_bug.cgi?id=773210

src/wayland/meta-window-wayland.c

@@ -117,6 +117,20 @@ static void
 meta_window_wayland_focus (MetaWindow *window,
                            guint32     timestamp)
 {
+  MetaWaylandSurface *surface = window->surface;
+  MetaWaylandSurfaceRoleShellSurface *shell_surface_role =
+     META_WAYLAND_SURFACE_ROLE_SHELL_SURFACE (surface->role);
+
+  /* The keyboard focus semantics for non-grabbing zxdg_shell_v6 popups
+   * is pretty undefined. Same applies for subsurfaces, but in practice,
+   * subsurfaces never receive keyboard focus, so it makes sense to
+   * do the same for non-grabbing popups.
+   *
+   * See https://bugzilla.gnome.org/show_bug.cgi?id=771694#c24
+   */
+  if (META_IS_WAYLAND_XDG_POPUP (shell_surface_role))
+    return;
+
   meta_display_set_input_focus_window (window->display,
                                        window,
                                        FALSE,