anchor.diff:    WebDriverPageLoaderElement get globalContext => _globalContext;
   
     @override
  -  Future getInstance(Type type, [dynamic context]) async {
  +  Future/*<T>*/ getInstance/*<T>*/(Type type, [dynamic context]) async {
       if (context != null) {
         if (context is wd.SearchContext) {
           context = new WebDriverPageLoaderElement(context, this);
  
positive.code: 
    @override
    Future<Rectangle> get offset async {
      var rect = await context.driver.execute(
          '''return {
            left: arguments[0].offsetLeft,
            top: arguments[0].offsetTop,
  
negative.code: 
    _WebElementPageLoaderElement(
        wd.WebElement _context, WebDriverPageLoader loader)
        : this.context = _context,
          this.attributes = new _ElementAttributes(_context),
          this.computedStyle = new _ElementComputedStyle(_context),
          this.style = new _ElementStyle(_context),
          super._(loader);
  
    @override
    Future<WebDriverPageLoaderElement> get shadowRoot async {
  