firefox 标签栏自动伸缩
Latest nightly build (Mozilla/5.0 (Windows; U; Windows NT 6.1; WOW64; en-US; rv:1.9.3a6pre) Gecko/20100625 Minefield/3.7a6pre)，当然只在标题栏塞满的情况下：
Latest nightly build (Mozilla/5.0 (Windows; U; Windows NT 6.1; WOW64; en-US; rv:1.9.3a6pre) Gecko/20100625 Minefield/3.7a6pre)，当然只在标题栏塞满的情况下：