anchor.diff:  
     // Current tab index.
     @HostBinding('attr.tabindex')
  +  @visibleForTemplate
     String get tabIndex => disabled ? "-1" : _defaultTabIndex;
   
     /// Current state of the checkbox. This is user set-able state, via
  
positive.code: )
  class MaterialCheckboxComponent
      implements ControlValueAccessor<bool>, HasDisabled, Focusable, OnDestroy {
    @HostBinding('class')
    static const hostClass = 'themeable';
  
  
negative.code:   }
  
    /// Current icon, depends on the state of [checked] and [indeterminate].
    @visibleForTemplate
    Icon get icon => _icon;
    Icon _icon = uncheckedIcon;
  
  