anchor.diff:                  [offsetX]="offsetX"
                   [offsetY]="offsetY"
                   [autoDismiss]="false"
  +                [class]="popupClassName"
                   [source]="popupSource"
                   role="tooltip">
     <div class="paper-container"
  
positive.code:   visibility: Visibility.all,
  )
  class MaterialPaperTooltipComponent implements DeferredContentAware, Tooltip {
    PopupSource _tooltipSource;
    PopupSource get popupSource => _tooltipSource;
  
  
negative.code: // BSD-style license that can be found in the LICENSE file.
  
  import 'dart:async';
  import 'dart:html';
  
  import 'package:angular/angular.dart';
  import 'package:angular_components/utils/angular/css/css.dart';
  import 'package:angular_components/content/deferred_content.dart';
  import 'package:angular_components/content/deferred_content_aware.dart';
  import 'package:angular_components/laminate/enums/alignment.dart';
  