when (listenerInstalledOn) {
      ListenerInstalledOn.Call -> {
        addEventListener(eventRecorder.eventListener)
      }

      ListenerInstalledOn.Relay -> {
        addEventListener(EventListenerRelay(this, eventRecorder).eventListener)
      }

      ListenerInstalledOn.Client -> {} // listener is added elsewhere.
    }
  }

  enum class ListenerInstalledOn {
    Client,
    Call,