The chrome extension for Girraween Countdown
This extension stops the need for you having the girraween countdown tab open all the time. The icon will change to show the time until the end of the lesson, and you can click the icon to see the classes you have for the day.
Note: this extension is now outdated. Please use the Class Countdown extension instead:
https://chrome.google.com/webstore/detail/class-countdown-extension/lompgalcaddbggjgbmicgimelihccdpe