dist/scripts/vendor.min.js
function(control, newName) {
    var oldName = control.$name;

    if (this[oldName] === control) {
      delete this[oldName];
    }
    this[newName] = control;
    control.$name = newName;
  }
function(control, newName) {
    var oldName = control.$name;

    if (this[oldName] === control) {
      delete this[oldName];
    }
    this[newName] = control;
    control.$name = newName;
  }
Private API: rename a form control