Comment 24 for bug 874250

The repeat info implies 1s or 1/10 of the SQL time could be saved by building the bug notification recipient set once. There are two general calls to find recipients, one for the bug, and the other for the structural subscriptions. I think the next optimisation would be to ensure that the notification recipient set is created once for this action/request because we know that the set cannot mutate after is it first created.