We currently clear the +1 / +2 review flags whenever a new revision is uploaded, but it's very common to +2 / nits. This either requires a round trip to the reviewer, or for the author to +2 the CL themselves.

Maybe we should instead configure the +2 to be sticky so that there is more visibility into who really reviewed a change, and so there is less overhead for review management.

Before just doing this, we should get signoff from the ChromeOS team.

Assigning to Richard, who inspired this by forgetting he had a +2 and was annoyed nobody was reviewing his CL.