Use the new private GtkWindow api to request
client-side decorations for menus.
https://bugzilla.gnome.org/show_bug.cgi?id=731187
gtk_window_set_resizable (GTK_WINDOW (priv->toplevel), FALSE);
gtk_window_set_mnemonic_modifier (GTK_WINDOW (priv->toplevel), 0);
+ _gtk_window_request_csd (GTK_WINDOW (priv->toplevel));
gtk_style_context_add_class (gtk_widget_get_style_context (priv->toplevel), "popup");
/* Refloat the menu, so that reference counting for the menu isn't