UserActivitiesView should limit search depth

[roysmith]

Imagine we ask for:

count = 10
main=False
draft=True
others=False

on a user with 1 million edits but none to draft space. We'll iterate through all 1 million edits trying to find 10 drafts. There should be some circuit breaker which cuts the search off before then. Maybe never examine more than 10*count?

[roysmith]

UserActivitiesView no longer exists, but the same issue applies to TimelineView.