anchor.diff:      scrollBehavior.isScrollable = source.isScrollable;
     }
   
  -  void didMount() {
  -    _indicatorAnimation.addListener(_indicatorAnimationUpdated);
  -    super.didMount();
  -  }
  -
  -  void didUnmount() {
  -    _indicatorAnimation.removeListener(_indicatorAnimationUpdated);
  -    super.didUnmount();
  -  }
  -
  -  void _indicatorAnimationUpdated() {
  -    setState(() {
  -    });
  -  }
  -
     AnimatedRect get _indicatorRect => _indicatorAnimation.variable as AnimatedRect;
   
     void _startIndicatorAnimation(int fromTabIndex, int toTabIndex) {
       _indicatorRect
  -      ..begin = _tabIndicatorRect(fromTabIndex)
  +      ..begin = (_indicatorRect.value == null ? _tabIndicatorRect(fromTabIndex) : _indicatorRect.value)
         ..end = _tabIndicatorRect(toTabIndex);
       _indicatorAnimation
         ..progress = 0.0
  
positive.code:         data: new IconThemeData(color: iconThemeColor),
          child: new DefaultTextStyle(
            style: textStyle,
            child: new TabBarWrapper(
              children: tabs,
              selectedIndex: selectedIndex,
              backgroundColor: backgroundColor,
              indicatorColor: indicatorColor,
              indicatorRect: _indicatorRect.value,
              textAndIcons: textAndIcons,
              isScrollable: isScrollable,
              onLayoutChanged: _layoutChanged
            )
          )
        )
  
negative.code: import 'package:sky/widgets/ink_well.dart';
  import 'package:sky/widgets/scrollable.dart';
  import 'package:sky/widgets/theme.dart';
  import 'package:sky/widgets/transitions.dart';
  import 'package:sky/widgets/framework.dart';
  import 'package:vector_math/vector_math.dart';
  
  