window-actor: Update mask on focus changes

We currently assume that the frame mask and -shape don't change with the
focus style. This is reasonable for the actual decoration, but not for
the window shadow that is expected to be more pronounced when focused.
We will eventually let the GTK+ theme draw the shadow of regular windows,
so update shape region and frame mask on focus changes.

https://bugzilla.gnome.org/show_bug.cgi?id=744667

src/compositor/meta-window-actor.c

@@ -284,6 +284,7 @@ window_appears_focused_notify (MetaWindow *mw,
                                GParamSpec *arg1,
                                gpointer    data)
 {
+  meta_window_actor_update_shape (META_WINDOW_ACTOR (data));
   clutter_actor_queue_redraw (CLUTTER_ACTOR (data));
 }