Expiration on Triaging day(s)

[cpaelzer]

After discussing with rbasak the current mode of "list all expired" bugs is bad in multiple ways.

• It is depressing for the current triager, who likely will not handle any of those
• We need to split this backlog among the server Team, but showing up every day hides what the daily triage duty is responsible for

After this change a Triager will only see those that he needs to take care of.

In many ways this is the same that we had initially with the un-triaged time that we had to cover.
Therefore we track the backlog in the same gdoc where we did already track the general triaging backlog.

[cpaelzer]

@powersj to be discussed in the IRC meeting today, but please take a look ahead if you can