code: function Utilities_tryFocus(elem, useSetActive, scroller) {
              var previousActiveElement = _Global.document.activeElement;
  
              if (elem === previousActiveElement) {
                  return true;
              }
  
              var simpleLogicForValidTabStop = (exports.getTabIndex(elem) >= 0);
              if (!simpleLogicForValidTabStop) {
                  return false;
              }
  
              if (useSetActive) {
                  exports._setActive(elem, scroller);
              } else {
                  elem.focus();
              }
  
              if (previousActiveElement !== _Global.document.activeElement) {
                  return true;
              }
              return false;
          }
docs: Tries to give focus to an element which is a tabstop (i.e. tabIndex >= 0).