function define(name, fun) {
    var obj = exportPath(name);
    var exports = fun();
    for (var propertyName in exports) {
      // Maybe we should check the prototype chain here? The current usage
      // pattern is always using an object literal so we only care about own
      // properties.
      var propertyDescriptor = Object.getOwnPropertyDescriptor(exports,
                                                               propertyName);
      if (propertyDescriptor)
        Object.defineProperty(obj, propertyName, propertyDescriptor);
    }
  }
@param {string} name
@param {!Function} fun