anchor.diff:  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';
   
  
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:     scrollBehavior.isScrollable = source.isScrollable;
    }
  
    AnimatedRect get _indicatorRect => _indicatorAnimation.variable as AnimatedRect;
  
    void _startIndicatorAnimation(int fromTabIndex, int toTabIndex) {
      _indicatorRect
        ..begin = (_indicatorRect.value == null ? _tabIndicatorRect(fromTabIndex) : _indicatorRect.value)
        ..end = _tabIndicatorRect(toTabIndex);
      _indicatorAnimation
        ..progress = 0.0
  