wayland: Update saved size when maximized/fullscreen

If a client issues a `move_resize()` request while the window is
maximized or fullscreen, update the saved size for when it will be
unmaximized/unfullscreened

Related: https://gitlab.gnome.org/GNOME/gtk/issues/1044

gdk/wayland/gdkwindow-wayland.c

@@ -3311,6 +3311,12 @@ gdk_window_wayland_move_resize (GdkWindow *window,
         }
     }
 
+  if (window->state & (GDK_WINDOW_STATE_FULLSCREEN | GDK_WINDOW_STATE_MAXIMIZED))
+    {
+      impl->saved_width = width;
+      impl->saved_height = height;
+    }
+
   /* If this function is called with width and height = -1 then that means
    * just move the window - don't update its size
    */