_getClumpIdForAuditRef(auditRef) {
    const scoreDisplayMode = auditRef.result.scoreDisplayMode;
    if (scoreDisplayMode === 'manual' || scoreDisplayMode === 'notApplicable') {
      return scoreDisplayMode;
    }

    if (ReportUtils.showAsPassed(auditRef.result)) {
      if (this._auditHasWarning(auditRef)) {
        return 'warning';
      } else {
        return 'passed';
      }
    } else {
      return 'failed';
    }
  }
Returns the id of the top-level clump to put this audit in.
@param {LH.ReportResult.AuditRef} auditRef
@return {TopLevelClumpId}