anchor.diff:      focusable = b;
     }
   
  +  String get role => _role;
  +
     /// The ARIA role of the dropdown button.
  -  String get role => _role;
     @Input()
     set role(String value) {
       assert(
  
positive.code: 
    bool _showButtonBorder;
  
    @Output('blur')
    Stream<FocusEvent> get onBlur => _blur.stream;
    final _blur = new StreamController<FocusEvent>(sync: true);
  
negative.code: /// A button styled specifically for dropdowns.
  ///
  /// By default, this button is rendered with a triangle icon and an underline.
  /// The component itself does not have a popup itself but can be used to build
  /// dropdowns that are not provided. Use `material-dropdown-select` for a
  /// component that has the same button style, and implements the dropdown
  /// itself.
  @Component(
    selector: 'dropdown-button',
    changeDetection: ChangeDetectionStrategy.OnPush,
  