Run closed_world2_test using the normal compiler pipeline.

tests/compiler/dart2js/inference/inference_test_helper.dart

Index: tests/compiler/dart2js/inference/inference_test_helper.dart
diff --git a/tests/compiler/dart2js/inference/inference_test_helper.dart b/tests/compiler/dart2js/inference/inference_test_helper.dart
index 0e766f681854e5269bb765a9322502bde758cf67..f1259cced2c060d2396e7af49ada465c30528603 100644
--- a/tests/compiler/dart2js/inference/inference_test_helper.dart
+++ b/tests/compiler/dart2js/inference/inference_test_helper.dart
@@ -31,7 +31,8 @@ checkCode(String annotatedCode, CheckMemberFunction checkMember,
   compiler.stopAfterTypeInference = true;
   Uri mainUri = Uri.parse('memory:main.dart');
   await compiler.run(mainUri);
-  compiler.mainApp.forEachLocalMember((member) {
+  LibraryElement mainApp = compiler.mainApp;
+  mainApp.forEachLocalMember((member) {
     if (member.isClass) {
       member.forEachLocalMember((member) {
         checkMember(compiler, expectedMap, member);