All code for this is part of the quitter project on GitHub: https://github.com/mozilla-extensions/quitter
This is within the mozilla-extensions organization so that we can sign the .xpi.
To update code, please submit a PR to the github repo. Once that is merged in, a JIRA ticket (e.g. ADDONSOPS-194 or ADDONSOPS-337) is needed to resign the .xpi.