Handle member closurization in closed_world2_test

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 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/closure.dart';
@@ skipping 34 matching lines @@
 import '../serialization/model_test_helper.dart';
 import '../serialization/test_helper.dart';
 
 import 'closed_world_test.dart';
 import 'impact_test.dart';
 
 const SOURCE = const {
   'main.dart': '''
 main() {
   print('Hello World');
+  ''.contains; // Trigger member closurization.
 }
 '''
 };
 
 main(List<String> args) {
   Arguments arguments = new Arguments.from(args);
   Uri entryPoint;
   Map<String, String> memorySourceFiles;
   if (arguments.uri != null) {
     entryPoint = arguments.uri;
@@ skipping 315 matching lines @@
       usage2.isInvokeOnUsed);
   check(usage1, usage2, 'isRuntimeTypeUsed', usage1.isRuntimeTypeUsed,
       usage2.isRuntimeTypeUsed);
   check(usage1, usage2, 'isIsolateInUse', usage1.isIsolateInUse,
       usage2.isIsolateInUse);
   check(usage1, usage2, 'isFunctionApplyUsed', usage1.isFunctionApplyUsed,
       usage2.isFunctionApplyUsed);
   check(usage1, usage2, 'isNoSuchMethodUsed', usage1.isNoSuchMethodUsed,
       usage2.isNoSuchMethodUsed);
 }