code: function Transition(path, retry) {
    this.path = path;
    this.abortReason = null;
    // TODO: Change this to router.retryTransition(transition)
    this.retry = retry.bind(this);
  }
docs: Encapsulates a transition to a given path.
  
  The willTransitionTo and willTransitionFrom handlers receive
  an instance of this class as their first argument.