anchor.diff:      shrinkWrap: shrinkWrap,
     );
   
  +  /// The amount of space by which to inset the children.
     final EdgeInsets padding;
   
     @override
  
positive.code:   /// On iOS, this identifies the scroll view that will scroll to top in
    /// response to a tap in the status bar.
    ///
    /// Defaults to true when `scrollDirection` is vertical and `controller` is
    /// not specified.
    final bool primary;
  
    final ScrollPhysics physics;
  
    final bool shrinkWrap;
  
    @protected
    AxisDirection getDirection(BuildContext context) {
      // TODO(abarth): Consider reading direction.
  
negative.code:     return null;
    }
  
    /// Subclasses should override this method to build the slivers for the inside
    /// of the viewport.
    @protected
    List<Widget> buildSlivers(BuildContext context);
  
  