function decorateElement(element) {
  const hasMissingTabIndex = Boolean(
    !element.getAttribute('tabindex') && element.tabIndex === -1,
  );

  if (hasMissingTabIndex) {
    elementsWithMissingTabIndex.push(element);
    element.tabIndex = 0;
  }
}
Decorates element with tabindex attributes
@param {HTMLElement} element
@return {Object}
@private