[gnome-control-center] display: Fix the two output UI to start with the current configuration

[Rui Matos <rtcm src gnome org>]

commit 6c4eb9fc862df9082dc817f5dd36a2f60ab2ea43
Author: Rui Matos <tiagomatos gmail com>
Date:   Fri Aug 25 15:08:18 2017 +0200

    display: Fix the two output UI to start with the current configuration
    
    gtk_stack_set_visible_child_name() doesn't actually make a child
    visible if the child widget isn't visible already which means we'd
    always start in the first ("join") stack page even if the currently
    applied configuration is one of the others.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=786767

 panels/display/cc-display-panel.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/panels/display/cc-display-panel.c b/panels/display/cc-display-panel.c
index c60896c..4101899 100644
--- a/panels/display/cc-display-panel.c
+++ b/panels/display/cc-display-panel.c
@@ -2026,6 +2026,8 @@ make_two_output_ui (CcDisplayPanel *panel)
   add_two_output_page (switcher, stack, "single", _("Single Display"),
                        "video-single-display-symbolic");
 
+  gtk_widget_show_all (stack);
+
   g_signal_connect_object (stack, "notify::visible-child-name",
                            G_CALLBACK (two_output_visible_child_changed),
                            panel, G_CONNECT_SWAPPED);