code: private boolean interpolationsDisagree(TrackPositionUpdate lastUpdate, TrackPositionUpdate currentUpdate) {
          long now = System.nanoTime();
          return Math.abs(interpolateTimeSinceUpdate(lastUpdate, now) - interpolateTimeSinceUpdate(currentUpdate, now)) >
                  slack.get();
      }
docs: Check whether we have diverged from what we would predict from the last update that was sent to a particular
  track position listener.
  
  @param lastUpdate the last update that was sent to the listener
  @param currentUpdate the latest update available for the same player
  
  @return {@code true }if the listener will have diverged by more than our permitted amount of slack, and so
  should be updated