rowClass = function(rowId, opt_payload) {
    /** @private {!Array<!lf.schema.Column>} */
    this.columns_ = columns;

    /** @private {!Array<!lf.schema.Index>} */
    this.indices_ = indices;

    // Placed here so that defaultPayload() can run correctly.
    rowClass.base(this, 'constructor', rowId, opt_payload);
  }
@param {number} rowId
@param {!Object=} opt_payload
@extends {lf.Row}
@constructor