Add kernel/closed_world2_test

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 '../common/backend_api.dart';
 import '../common_elements.dart' show CommonElements, ElementEnvironment;
 import '../elements/elements.dart';
 import '../elements/entities.dart';
 import '../elements/resolution_types.dart';
 import '../elements/types.dart';
@@ skipping 195 matching lines @@
       : super(options, elementEnvironment, commonElements, helpers,
             backendClasses);
 
   void _registerBackendUse(FunctionEntity element) {
     _backendUsageBuilder.registerBackendFunctionUse(element);
     _backendUsageBuilder.registerGlobalFunctionDependency(element);
   }
 
   WorldImpact processNativeClasses(Iterable<LibraryEntity> libraries) {
     WorldImpactBuilderImpl impactBuilder = new WorldImpactBuilderImpl();
-    Set<ClassEntity> nativeClasses =
+    Iterable<ClassEntity> nativeClasses =
         _nativeClassResolver.computeNativeClasses(libraries);
     _nativeClasses.addAll(nativeClasses);
     _unusedClasses.addAll(nativeClasses);
     if (!enableLiveTypeAnalysis) {
       _registerTypeUses(impactBuilder, _nativeClasses, 'forced');
     }
     return impactBuilder;
   }
 
   void logSummary(void log(String message)) {
@@ skipping 84 matching lines @@
         emitter.directSubtypes.putIfAbsent(superclass, () => <ClassEntity>[]);
     directSubtypes.add(cls);
   }
 
   void logSummary(void log(String message)) {
     super.logSummary(log);
     log('Compiled ${_registeredClasses.length} native classes, '
         '${_unusedClasses.length} native classes omitted.');
   }
 }