All strong mode cleaning of dart2js.

tests/compiler/dart2js/kernel/closed_world2_test.dart

 // Copyright (c) 2017, 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.
 
 // Partial test that the closed world computed from [WorldImpact]s derived from
 // kernel is equivalent to the original computed from resolution.
 library dart2js.kernel.closed_world2_test;
 
 import 'dart:async';
 
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/common.dart';
 import 'package:compiler/src/common_elements.dart';
 import 'package:compiler/src/compiler.dart';
-import 'package:compiler/src/elements/resolution_types.dart';
 import 'package:compiler/src/elements/types.dart';
 import 'package:compiler/src/enqueue.dart';
 import 'package:compiler/src/js_backend/backend_usage.dart';
 import 'package:compiler/src/kernel/element_map_impl.dart';
 import 'package:compiler/src/kernel/kernel_strategy.dart';
 import 'package:compiler/src/serialization/equivalence.dart';
 import 'package:compiler/src/universe/world_builder.dart';
 import 'package:compiler/src/util/util.dart';
 import 'package:compiler/src/world.dart';
 import 'package:expect/expect.dart';
@@ skipping 115 matching lines @@
   ResolutionEnqueuer enqueuer2 = compiler2.enqueuer.resolution;
   ClosedWorld closedWorld2 = compiler2.resolutionWorldBuilder.closeWorld();
   BackendUsage backendUsage2 = closedWorld2.backendUsage;
 
   checkNativeClasses(compiler1, compiler2, strategy);
 
   checkBackendUsage(backendUsage1, backendUsage2, strategy);
 
   checkResolutionEnqueuers(backendUsage1, backendUsage2, enqueuer1, enqueuer2,
       elementEquivalence: (a, b) => equivalence.entityEquivalence(a, b),
-      typeEquivalence: (ResolutionDartType a, DartType b) {
+      typeEquivalence: (DartType a, DartType b) {
         return equivalence.typeEquivalence(unalias(a), b);
       },
       elementFilter: elementFilter,
       verbose: arguments.verbose);
 
   checkClosedWorlds(closedWorld1, closedWorld2,
       strategy: equivalence.defaultStrategy, verbose: arguments.verbose);
 
   return ResultKind.success;
 }