[gtk/menu-section-title] popovermenu: Reinstate section title handling

[Matthias Clasen <matthiasc src gnome org>]

commit 79267674fffb7c60f6afcdc0b7d29318a8110646
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Apr 17 13:53:56 2020 -0400

    popovermenu: Reinstate section title handling
    
    We were creating a hbox with separators around the label,
    but forgot to arrange sizing to prevent the separators from
    shrinking into nothingness.

 gtk/gtkmenusectionbox.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/gtk/gtkmenusectionbox.c b/gtk/gtkmenusectionbox.c
index 16d5061b4a1..7933f81dfa0 100644
--- a/gtk/gtkmenusectionbox.c
+++ b/gtk/gtkmenusectionbox.c
@@ -618,6 +618,7 @@ gtk_menu_section_box_new_section (GtkMenuTrackerItem *item,
       separator = gtk_separator_new (GTK_ORIENTATION_HORIZONTAL);
       gtk_widget_set_valign (separator, GTK_ALIGN_CENTER);
       gtk_container_add (GTK_CONTAINER (box->separator), separator);
+      gtk_size_group_add_widget (box->indicators, separator);
 
       title = gtk_label_new (label);
       g_object_bind_property (item, "label", title, "label", G_BINDING_SYNC_CREATE);
@@ -627,6 +628,7 @@ gtk_menu_section_box_new_section (GtkMenuTrackerItem *item,
 
       separator = gtk_separator_new (GTK_ORIENTATION_HORIZONTAL);
       gtk_widget_set_valign (separator, GTK_ALIGN_CENTER);
+      gtk_widget_set_hexpand (separator, TRUE);
       gtk_container_add (GTK_CONTAINER (box->separator), separator);
     }
   else