wayland: Move out gtk_shell from meta-wayland-surface.c

https://bugzilla.gnome.org/show_bug.cgi?id=769936

src/wayland/meta-wayland-gtk-shell.h

@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#ifndef META_WAYLAND_GTK_SHELL_H
+#define META_WAYLAND_GTK_SHELL_H
+
+#include "wayland/meta-wayland.h"
+
+void meta_wayland_gtk_shell_init (MetaWaylandCompositor *compositor);
+
+#endif /* META_WAYLAND_GTK_SHELL_H */