Revert "Widget: Remove obsolete hack-arounds for HandleBox"

This reverts commit 12805a4fbf.

I must have been looking at the wrong tree because HandleBox is only
deprecated in GTK+ 3, not removed.

gtk/gtkwidget.c

@@ -6321,6 +6321,9 @@ gtk_widget_translate_coordinates (GtkWidget  *src_widget,
       src_y = dy;
 
       window = gdk_window_get_effective_parent (window);
+
+      if (!window)		/* Handle GtkHandleBox */
+	return FALSE;
     }
 
   /* And back */
@@ -6330,6 +6333,12 @@ gtk_widget_translate_coordinates (GtkWidget  *src_widget,
       dest_list = g_list_prepend (dest_list, window);
 
       window = gdk_window_get_effective_parent (window);
+
+      if (!window)		/* Handle GtkHandleBox */
+        {
+          g_list_free (dest_list);
+          return FALSE;
+        }
     }
 
   while (dest_list)