.length - 1].end;
    }

    /**
     * @returns {boolean}
     */
    isHeavy() {
      return this.end - this.start > TASK_CLUSTER_HEAVINESS_THRESHOLD_MS;
    }
  }


  /**
   * Returns all the task clusters of |sortedLongTasks|.
   *
   * @param {Array.<!tr.model.TimedEvent>} sortedLongTasks - Main thread tasks
   *     longer than 50ms, sorted by task start time.
   * @returns {Array.<!TaskCluster>}
   */
  function findFCITaskClusters(sortedLongTasks) {
    const clusters = [];
    if (sortedLongTasks.