function compareParsedOpIds(id1, id2) {
  if (id1.counter < id2.counter) return -1
  if (id1.counter > id2.counter) return +1
  if (id1.actorId < id2.actorId) return -1
  if (id1.actorId > id2.actorId) return +1
  return 0
}
Comparison function to pass to Array.sort(), which compares two opIds in the
form produced by `actorIdToActorNum` so that they are sorted in increasing
Lamport timestamp order (sorted first by counter, then by actorId).