 task to a fresh cluster.
        clusters.push(new TaskCluster(currentClusterTasks));
        currentClusterTasks = [currTask];
      }
    }

    clusters.push(new TaskCluster(currentClusterTasks));

    return clusters;
  }

  /**
   * Returns true if at time |timestamp|, assuming |timestamp| is not in the
   * middle of a heavy task cluster, we have a long enough quiet window for
   * determining First CPU Idle.
   *
   * @param {number} timestamp - Timestamp of interest. We assume |timestamp| is
   *  