merge = function(one, two) {
  var result = {};
  mergeInto(result, one);
  mergeInto(result, two);
  return result;
}
Shallow merges two structures into a return value, without mutating either.

@param {?object} one Optional object with properties to merge from.
@param {?object} two Optional object with properties to merge from.
@return {object} The shallow extension of one by two.