Cookies google CheckCookie链接做什么？

我发现一段代码，在以编程方式登录google帐户后打开此链接。
这个链接的目的是什么

要查看更改cookie的实时演示，请使用firefox中的firecookie插件

After Successfully logged in this url gets all old cookiees which stored in browser in request header and verify with server and update it if any changes.

generally this cookie always changed during each request 

 1. __utma,
 2. __utmb,
 3. __utmc,
 4. __utmz.