anchor.diff:  library spark_widgets.splitter;
   
   import 'dart:html';
  +import 'dart:async';
   import 'package:polymer/polymer.dart';
   
   @CustomTag('spark-splitter')
  
positive.code:   }
  
    void dragEnd(MouseEvent e) {
      classes.remove('active');
      _isDragged = false;
    }
  }
  
negative.code:   bool _isNext;
    bool _horizontal;
    int _dimension;
    StreamSubscription<MouseEvent> _dragSubscr;
    StreamSubscription<MouseEvent> _dragEndSubscr;
  
    SparkSplitter.created() : super.created() {
      onMouseDown.listen(dragStart);
      // TODO(sergeygs): Switch to using onDrag* instead of onMouse* once support
      // onDrag* are fixed (as of 2013-11-13 they don't work).
      //onDragStart.listen(dragStart);
  
      directionChanged();
    }
  