[gnome-flashback] input-sources: use GtkButtonBox for buttons box

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 0ce05f68c97fa16c7ac0d9238d131c45546fc706
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Mon Jan 18 14:10:39 2016 +0200

    input-sources: use GtkButtonBox for buttons box

 .../libinput-sources/gf-candidate-area.c           |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/gnome-flashback/libinput-sources/gf-candidate-area.c 
b/gnome-flashback/libinput-sources/gf-candidate-area.c
index 87a18be..9f088ff 100644
--- a/gnome-flashback/libinput-sources/gf-candidate-area.c
+++ b/gnome-flashback/libinput-sources/gf-candidate-area.c
@@ -149,10 +149,12 @@ gf_candidate_area_init (GfCandidateArea *area)
                         G_CALLBACK (button_clicked_cb), area);
     }
 
-  area->button_box = gtk_box_new (GTK_ORIENTATION_HORIZONTAL, 0);
+  area->button_box = gtk_button_box_new (0);
   gtk_container_add (GTK_CONTAINER (area), area->button_box);
   gtk_widget_show (area->button_box);
 
+  gtk_button_box_set_layout (GTK_BUTTON_BOX (area->button_box), GTK_BUTTONBOX_EXPAND);
+
   size = GTK_ICON_SIZE_BUTTON;
 
   area->prev_button = gtk_button_new ();