git cl split calls /changes/{change-id}/revisions/{revision-id}/review after uploading a CL to add a comment.

We should look if it is possible to send this as a git push option in order to:
 * Decrease latency
 * Eliminate possibility of hitting stale Gerrit/Git replica in post-push HTTP requests
 * Decrease load on the server
 * Simplify semantics: state of the change can't change between the first and second request
 * Allow emails to reflect the full set of things that happened
 * Prevent the possibility of interruption between first and second step

See also  crbug.com/877717