[gtk/wip/baedert/for-master] popover: Use gtk_widget_add_css_class

[Timm Bäder <baedert src gnome org>]

commit 76f2396764c67427ba801105729ec56ba82703e7
Author: Timm Bäder <mail baedert org>
Date:   Sat Aug 1 10:31:38 2020 +0200

    popover: Use gtk_widget_add_css_class

 gtk/gtkpopover.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
---
diff --git a/gtk/gtkpopover.c b/gtk/gtkpopover.c
index d77d225a1e..e670d7f40c 100644
--- a/gtk/gtkpopover.c
+++ b/gtk/gtkpopover.c
@@ -870,8 +870,7 @@ gtk_popover_init (GtkPopover *popover)
   gtk_widget_set_layout_manager (priv->contents_widget, gtk_bin_layout_new ());
   gtk_widget_set_parent (priv->contents_widget, GTK_WIDGET (popover));
 
-  gtk_css_node_add_class (gtk_widget_get_css_node (GTK_WIDGET (popover)),
-                          g_quark_from_static_string (GTK_STYLE_CLASS_BACKGROUND));
+  gtk_widget_add_css_class (widget, "background");
 
   add_actions (popover);
 }