该版本在视觉效果上做了不少改进，以及修复了一些bug。
下载地址：http://ftp.gnome.org/pub/GNOME/sources/gnome-shell/2.91
Changes since 2.91.1
====================
* Use GNOME 3 WM theme by default [Jon McCann]
* Add general keyboard focus support to the Shell Toolkit [Dan]
* Support new notification spec 'action-icons' to turn on icon buttons.
[Jonathan Matthew]
* Pay attention to the distance the mouse has moved from the
message tray when deciding how quickly to hide the tray [Hellyna]
* Change magnifier defaults to be full screen [Florian]
* Fix creating many one-shot Clutter materials and compiling many
shader programs per frame [Neil]
* Visual tweaks [Adel, Dan, Jon McCann]
* Bug fixes [Florian, Giovanni, Owen]
* Build fixes [Dan, Florian, Jon McCann, Mathieu]
