function isFocusableAlternativeImpl(element) {
  element.focus();
  return document.activeElement == element &&  // programmatically focusable
      element.tabIndex >= 0;  // keyboard focusing is not disabled
}
Simple alternative implementation of googDom.isFocusable. Serves as a sanity
check whether the tests are correct. Unfortunately it can't replace the real
implementation because of the side effects.
@param {!Element} element
@return {boolean}
@suppress {strictMissingProperties} suppression added to enable type checking