Missing Power Off Icon on Debian wheezy

I have no idea why, but I faced with the fact that there is no icon about shutdown in the menu showed by click username at the right-top Desktop. I found how to show Power Off icon.

1. apt-get install gnome-tweak-tool
2. apt-get install gnome-shell-extensions
3. reboot
4. check Enabled Shell Extensions
   1. launch Activities->Applications->Advanced Settings
   2. click Shell Extensions
   3. check if Alternative Status Menu Extension, if disabled, turn on

Reference sites are below.

• [SOLVED] Missing Shutdown Options from Gnome - Wheezy 7.1
• GNOME / gnome-shell-extensions · GitLab