anchor.diff:  import 'dart:mirrors';
   
   import 'package:polymer/polymer.dart';
  -import 'package:polymer_elements/polymer_selection/polymer_selection.dart' show PolymerSelection;
  +//import 'package:polymer_elements/polymer_selection/polymer_selection.dart' show PolymerSelection;
   
   @CustomTag('polymer-selector')
   class PolymerSelector extends PolymerElement {
  
positive.code:       }
        target = target.parentNode;
      }
    }
    
  }
  
negative.code:   MutationObserver _observer;
    
    Stream<CustomEvent> get onPolymerSelect {
      Element selection = $['selection'];
      if(selection != null) {
        // TODO return selection.onPolymerSelect;
      }
  