Revert "Move towards using WorldImpact for codegen"

pkg/compiler/lib/src/native/enqueue.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:collection' show Queue;
 
 import '../common.dart';
 import '../common/backend_api.dart' show ForeignResolver;
 import '../common/registry.dart' show Registry;
 import '../common/resolution.dart' show Resolution;
@@ skipping 29 matching lines @@
   // something like `computeNativeField`.
   /// Process the potentially native [field]. Adds information from metadata
   /// attributes.
   void handleFieldAnnotations(Element field) {}
 
   /// Process the potentially native [method]. Adds information from metadata
   /// attributes.
   void handleMethodAnnotations(Element method) {}
 
   /// Returns whether native classes are being used.
-  bool get hasInstantiatedNativeClasses => false;
+  bool hasInstantiatedNativeClasses() => false;
 
   /// Emits a summary information using the [log] function.
   void logSummary(log(message)) {}
 
   // Do not use annotations in dart2dart.
   ClassElement get annotationCreatesClass => null;
   ClassElement get annotationReturnsClass => null;
   ClassElement get annotationJsNameClass => null;
 }
 
 abstract class NativeEnqueuerBase implements NativeEnqueuer {
   static final RegExp _identifier = new RegExp(r'^[a-zA-Z_$][a-zA-Z0-9_$]*$');
 
   /**
    * The set of all native classes.  Each native class is in [nativeClasses] and
    * exactly one of [unusedClasses], [pendingClasses] and [registeredClasses].
    */
   final Set<ClassElement> nativeClasses = new Set<ClassElement>();
 
   final Set<ClassElement> registeredClasses = new Set<ClassElement>();
   final Set<ClassElement> pendingClasses = new Set<ClassElement>();
   final Set<ClassElement> unusedClasses = new Set<ClassElement>();
 
   final Set<LibraryElement> processedLibraries;
 
-  bool get hasInstantiatedNativeClasses => !registeredClasses.isEmpty;
+  bool hasInstantiatedNativeClasses() => !registeredClasses.isEmpty;
 
   final Set<ClassElement> nativeClassesAndSubclasses = new Set<ClassElement>();
 
   final Map<ClassElement, Set<ClassElement>> nonNativeSubclasses =
       new Map<ClassElement, Set<ClassElement>>();
 
   /**
    * Records matched constraints ([SpecialType] or [DartType]).  Once a type
    * constraint has been matched, there is no need to match it again.
    */
@@ skipping 586 matching lines @@
     List<Element> directSubtypes =
         emitter.directSubtypes.putIfAbsent(superclass, () => <ClassElement>[]);
     directSubtypes.add(cls);
   }
 
   void logSummary(log(message)) {
     log('Compiled ${registeredClasses.length} native classes, '
         '${unusedClasses.length} native classes omitted.');
   }
 }