[gtk] TreeMenu: Don't manually reinvent g_list_index()

[Daniel Boles <dboles src gnome org>]

commit 3194c394717e38fec0b74a46ffc01f47d2bde1bc
Author: Daniel Boles <dboles src gmail com>
Date:   Sat Oct 20 15:19:11 2018 +0100

    TreeMenu: Don't manually reinvent g_list_index()
    
    g_list_index() "Gets the position of the element containing the given
    data (starting from 0)." That is exactly what we were manually doing.

 gtk/gtktreemenu.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)
---
diff --git a/gtk/gtktreemenu.c b/gtk/gtktreemenu.c
index 6fb513d24f..80db15419f 100644
--- a/gtk/gtktreemenu.c
+++ b/gtk/gtktreemenu.c
@@ -876,18 +876,11 @@ static gint
 menu_item_position (GtkTreeMenu *menu,
                     GtkWidget   *item)
 {
-  GList *children, *l;
+  GList *children;
   gint   position;
 
   children = gtk_container_get_children (GTK_CONTAINER (menu));
-  for (position = 0, l = children; l; position++, l = l->next)
-    {
-      GtkWidget *iitem = l->data;
-
-      if (item == iitem)
-        break;
-    }
-
+  position = g_list_index (children, item);
   g_list_free (children);
 
   return position;