Merge branch 'gtk-demo-fixes' into 'master'

Gtk demo fixes

See merge request GNOME/gtk!1266

diff --cc gtk/gtktreeview.c
index e395d51da8fd8ace881634cdb5904a1c0982b5c7,291e7abc66960532b935675971a6d5f3e7e7f6c0..a4aeccc1be7c7fe989a11920b3f0738e2340971e
--- 1/gtk/gtktreeview.c
--- 2/gtk/gtktreeview.c
+++ b/gtk/gtktreeview.c
@@@ -8173,8 -8193,11 +8173,11 @@@ gtk_tree_view_put (GtkTreeView       *t
    child->column = column;
    child->border = *border;
  
 -  tree_view->priv->children = g_list_append (tree_view->priv->children, child);
 +  tree_view->children = g_list_append (tree_view->children, child);
  
+   gtk_css_node_insert_after (gtk_widget_get_css_node (GTK_WIDGET (tree_view)),
+                              gtk_widget_get_css_node (child_widget),
+                              tree_view->priv->header_node);
    gtk_widget_set_parent (child_widget, GTK_WIDGET (tree_view));
  }