[gtk+] Fix the build

[Matthias Clasen <matthiasc src gnome org>]

commit 08a0257893493f888b503db8b18d0c31c2e35f60
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Mar 21 12:10:44 2016 -0400

    Fix the build

 gtk/gtkshortcutswindow.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkshortcutswindow.c b/gtk/gtkshortcutswindow.c
index 4a1b5bc..0bea2ce 100644
--- a/gtk/gtkshortcutswindow.c
+++ b/gtk/gtkshortcutswindow.c
@@ -827,7 +827,7 @@ gtk_shortcuts_window_init (GtkShortcutsWindow *self)
                                                        NULL),
                                 "visible", TRUE,
                                 NULL);
-  gtk_style_context_add (gtk_widget_get_style_context (search_button), "image-button");
+  gtk_style_context_add_class (gtk_widget_get_style_context (GTK_WIDGET (search_button)), "image-button");
   gtk_container_add (GTK_CONTAINER (priv->header_bar), GTK_WIDGET (search_button));
 
   priv->main_box = g_object_new (GTK_TYPE_BOX,