archlinux yaourt 更新包

Question

请问archlinux系统，如何更新yaourt安装的包

比如google-chrome 用命令查看有新版

yaourt -Ss google-chrome

archlinuxcn/google-chrome 51.0.2704.106-1 [installed]
    An attempt at creating a safer, faster, and more stable browser (Stable Channel)
archlinuxcn/google-chrome-dev 53.0.2785.8-1
    An attempt at creating a safer, faster, and more stable browser (Dev Channel)
aur/google-chrome 52.0.2743.82-1 [installed: 51.0.2704.106-1] (Out of Date) (1323) (33.83)
    An attempt at creating a safer, faster, and more stable browser (Stable Channel)
aur/google-chrome-beta 53.0.2785.34-1 (327) (3.09)
    An attempt at creating a safer, faster, and more stable browser (Beta Channel)
aur/google-chrome-dev 54.0.2810.2-1 (594) (3.32)
    An attempt at creating a safer, faster, and more stable browser (Dev Channel)

yaourt -Syu --aur 
更新没有改变

请问该如何操作？