[mutter] wayland: Check serial on wp_tablet_pad_ring.set_feedback

[Carlos Garnacho <carlosg src gnome org>]

commit 4f250574131873caba17c63fc693f8bfd851e17e
Author: Carlos Garnacho <carlosg gnome org>
Date:   Wed Jun 29 18:10:18 2016 +0200

    wayland: Check serial on wp_tablet_pad_ring.set_feedback

 src/wayland/meta-wayland-tablet-pad-ring.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/wayland/meta-wayland-tablet-pad-ring.c b/src/wayland/meta-wayland-tablet-pad-ring.c
index ee138e0..26ff557 100644
--- a/src/wayland/meta-wayland-tablet-pad-ring.c
+++ b/src/wayland/meta-wayland-tablet-pad-ring.c
@@ -79,7 +79,8 @@ tablet_pad_ring_set_feedback (struct wl_client   *client,
 {
   MetaWaylandTabletPadRing *ring = wl_resource_get_user_data (resource);
 
-  /* FIXME: check serial */
+  if (ring->group->mode_switch_serial != serial)
+    return;
 
   ring->feedback = g_strdup (str);
 }