widget: Mark the size as changed when it changes

This notifies the AT context that the widgets size
has changed.

gtk/gtkwidget.c

@@ -3811,7 +3811,6 @@ gtk_widget_allocate (GtkWidget    *widget,
 
   gtk_widget_adjust_size_allocation (widget, &adjusted);
 
-
   if (adjusted.width < 0 || adjusted.height < 0)
     {
       g_warning ("gtk_widget_size_allocate(): attempt to allocate %s %s %p with width %d and height %d",
@@ -3907,6 +3906,9 @@ gtk_widget_allocate (GtkWidget    *widget,
 
   gtk_widget_update_paintables (widget);
 
+  if (size_changed)
+    gtk_accessible_bounds_changed (GTK_ACCESSIBLE (widget));
+
 skip_allocate:
   if (size_changed || baseline_changed)
     gtk_widget_queue_draw (widget);