function setPopupParentElement(el) {
  inputDatePicker = new InputDatePicker(dateTimeFormatter, dateTimeParser);

  if (el) {
    inputDatePicker.setPopupParentElement(el);
  }

  inputDatePicker.render(dom.getElement('renderElement'));
  /** @suppress {visibility} suppression added to enable type checking */
  popupDatePicker = inputDatePicker.popupDatePicker_;
}
Creates a new InputDatePicker and calls setPopupParentElement with the
specified element, if provided. If el is null, then setPopupParentElement
is not called.
@param {Element} el If non-null, the argument to pass to
    inputDatePicker.setPopupParentElement().