anchor.diff:    bool get checked => _checked;
     bool _checked = false;
   
  +  /// Whether the checkbox can be changed by user interaction.
     @Input()
     bool readOnly = false;
   
  
positive.code:   final _onChecked = new StreamController.broadcast();
  
    /// Fired when checkbox goes in and out of indeterminate state, but not when
    /// set to checked. Sends the state of [indeterminate];
    @Output('indeterminateChange')
    Stream get onIndeterminate => _onIndeterminate.stream;
    final _onIndeterminate = new StreamController.broadcast();
  
negative.code:   Icon get icon => _icon;
    Icon _icon = uncheckedIcon;
  
    /// Color of the checkbox and ripple when checked.
    ///
    /// Example: '#FF00FF'. By default it is $mat-blue-500. Note that the
    /// themeColor is applied to the checkbox even when the box is unchecked,
    /// which deviates from the standard material spec. Use mixin to set
    /// themeColor unless you want this behavior.
    @Input()
    String themeColor;
  
  