anchor.diff:  /// A button styled specifically for dropdowns.
   ///
   /// By default, this button is rendered with a triangle icon and an underline.
  -///
  -/// __Properties:__
  -///
  -///  - `iconName: String` -- Material icon displayed on the right of the button.
  -///   Defaults to `arrow_drop_down`.
  -///  - `icon: Icon` -- `Icon` model instance.
  -///  - `buttonText: String` -- Text on the button.
  -///  - `buttonAriaLabel: String` - Optional aria label for the button.
  -///  - `showButtonBorder: bool` - Whether to show the bottom border of the
  -///   dropdown button.
  -///  - `disabled: bool` - Whether the button should be disabled.
  -///
  -/// __Events:__
  -///
  -/// - `trigger: Event` -- Published when the button is activated via click or
  -///   keypress.
  +/// 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,
  
positive.code:     _blur.add(event);
    }
  
    @Output()
    Stream<UIEvent> get trigger => _button.trigger;
  }
  
negative.code: 
    bool _showButtonBorder;
  
    /// Event that fires when the dropdown button is blurred.
    @Output('blur')
    Stream<FocusEvent> get onBlur => _blur.stream;
    final _blur = new StreamController<FocusEvent>(sync: true);
  