In the CQ exonerator, start tracking CLs that exonerator decided to exonerate, but where the user had already taken the exact action that exonerator was going to take -- i.e., marke CQ:+1.
This shouldn't include other user actions like a new patch set.

This metric is one way of measuring user impatience with the CQ, and as our CQ becomes more responsive and trusted, this metric should fall (people won't be in the habit of hitting CQ:+1 on failures, and only exonerator will exonerate CLs based on more knowledge than the average user)