Similarly to bug 1510949, we can convert all protocol.js Actors to use ES Classes. It should be easier as there is no custom/preEvent special cases. And it should help implementing actor inheritance for the target actors.

In bug 1512154, I had to workaround the fact that Actors weren't using ES Classes yet. Because of that I had to duplicate Pool's contructor into Actor.initialize method: // Repeat Pool.constructor here as we can't call it from initialize // This is to be removed once actors switch to es classes and are able to call // Actor's contructor. if (conn) { this.conn = conn; } We should remember here to remove that and instead call super(conn) once initialize becomes Actor.constructor.