function openDatabaseStub(name, version, desc, size, opt_callback) {
  if (opt_callback != null) {
    opt_callback(upgradeDb);
  }
  return upgradeDb;
}
@param {string} name
@param {string} version
@param {string} desc
@param {number} size
@param {!function(?Database)=} opt_callback
@return {?Database}