anchor.diff:      _display = machine.newState('display');
       _cooling = machine.newState('cooling');
   
  -    _waiting.onStream(root.onMouseOver, (Event event) {
  +    _waiting.onStream(root.onMouseOver, (MouseEvent event) {
         Element element = event.target;
         if (element.dataset.containsKey(dataKey)) {
           _element = element;
  
positive.code:   /// The data key used to retrieve the tooltip text.
    final String dataKey;
  
    /// The CSS class applied to the tooltip its style.
    final String baseCssClass;
  
    /// The CSS class applied to the tooltip to show it.
  
negative.code:   final Machine machine = new Machine();
  
    /// Various (internal) states of the tooltip machine.
    State _waiting, _heating, _display, _cooling;
  
    /// The currently active element.
    Element _element;
  