The icon is called window-close-symbolic.
priv->gdk_type_hint == GDK_WINDOW_TYPE_HINT_NORMAL)
{
button = gtk_button_new ();
- image = gtk_image_new_from_icon_name ("window-delete-symbolic", GTK_ICON_SIZE_MENU);
+ image = gtk_image_new_from_icon_name ("window-close-symbolic", GTK_ICON_SIZE_MENU);
gtk_style_context_add_class (gtk_widget_get_style_context (button), "titlebutton");
g_object_set (image, "use-fallback", TRUE, NULL);
gtk_container_add (GTK_CONTAINER (button), image);