anchor.diff:  
   import 'dart:async' show Future;
   
  -import 'package:widgets/framework.dart' as flutter show Element, RenderElement;
  -import 'package:widgets/bindings.dart' as flutterWidgetBindings
  -    show WidgetBinding;
  +import 'package:flutter/widgets.dart' as flutter show Element, RenderObjectElement;
  +
  +import 'package:flutter/src/rendering/binding.dart' as flutterWidgetBindings
  +    show RendererBinding;
  +import 'package:flutter/src/widgets/binding.dart' as flutterWidgetBindings
  +    show WidgetsBinding;
   
   List<Map<String, dynamic>> stack;
   
   flutter.Element tree =
  -    flutterWidgetBindings.WidgetBinding.instance.renderViewElement;
  +    flutterWidgetBindings.WidgetsBinding.instance.renderViewElement;
   // the root of the element tree
   
   push(Map<String, dynamic> e) {
  
positive.code:   return {
      'type': mapType(e.runtimeType),
      'widget': mapWidget(e.widget),
      'isRenderElement': e is flutter.RenderElement,
      'renderObject': mapRenderObject(e.renderObject)
    };
  }
  
negative.code: }
  
  main() {
    flutterWidgetBindings.WidgetsBinding.instance.registerServiceExtension(
        name: 'returnElementTree', callback: debugReturnElementTree);
    flutterWidgetBindings.WidgetsBinding.instance.registerServiceExtension(
        name: 'returnWidgetTree', callback: debugReturnWidgetTree);
    // to be added to WidgetBinding.initServiceExtensions
  
    flutterWidgetBindings.RendererBinding.instance.registerServiceExtension(
        name: 'returnRenderObjectTree', callback: debugReturnRenderObjectTree);
    // to be added to RenderBinding.initServiceExtensions
  }
  