message: Call `on_new_vote` when vertex is ready to add.
diff: @@ -132,8 +132,18 @@ impl<C: Context> ConsensusProtocol<C::ConsensusValue> for HighwayProtocol<C> {
  }
  Ok(SynchronizerEffect::RequeueVertex(vertices)) => {
  new_vertices.extend(vertices);
  - let msg = HighwayMessage::NewVertex(v);
  // TODO: Add new vertex to state. (Indirectly, via synchronizer?)
  + // TODO: Handle effects from `highway.on_new_vote`.
  + let _additional_effects = match &v {
  + Vertex::Vote(swv) => {
  + self.highway.on_new_vote(&swv.hash(), swv.wire_vote.instant)
  + }
  + Vertex::Evidence(_) => {
  + // Do nothing?
  + vec![]
  + }
  + };
  + let msg = HighwayMessage::NewVertex(v);
  // TODO: Don't `unwrap`.
  let serialized_msg = serde_json::to_vec_pretty(&msg).unwrap();
  effects.push(ConsensusProtocolResult::CreatedGossipMessage(
  