[mutter/wayland] ui: restrict gtk to only use the x11 backend

[Giovanni Campagna <gcampagna src gnome org>]

commit 4fd3c63da9b68b47ad74534e2fec18399657e03a
Author: Giovanni Campagna <gcampagn redhat com>
Date:   Mon Aug 19 13:01:55 2013 +0200

    ui: restrict gtk to only use the x11 backend
    
    We use GTK as a way to get the X11 connection for our internal
    use, so we need it to keep using X.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=706303

 src/ui/ui.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/src/ui/ui.c b/src/ui/ui.c
index fc6fb4d..ed2c66d 100644
--- a/src/ui/ui.c
+++ b/src/ui/ui.c
@@ -56,6 +56,8 @@ struct _MetaUI
 void
 meta_ui_init (void)
 {
+  gdk_set_allowed_backends ("x11");
+
   if (!gtk_init_check (NULL, NULL))
     meta_fatal ("Unable to open X display %s\n", XDisplayName (NULL));
 }