Immediately logged out after changing timeout

1. Start with Automated Logout's timeout set to Disabled. (e.g., first-time install)
2. Go to User Settings page.
3. Wait 30+ seconds.
4. Change timeout to 30 seconds and submit. You will be immediately logged out.

The preferred behavior would be that the timeout counter resets after any timeout change. This problem will generally occur if you change to a lower timeout and you've already been on the User Settings page longer than that new timeout.

This was seen in Fx 3.0.11.