Run closed_world2_test using the normal compiler pipeline.

tests/compiler/dart2js/assert_message_throw_test.dart

Index: tests/compiler/dart2js/assert_message_throw_test.dart
diff --git a/tests/compiler/dart2js/assert_message_throw_test.dart b/tests/compiler/dart2js/assert_message_throw_test.dart
index 530e4040a2c05789a1b7f0dfc9faaedd7740f57d..729515388d12bf8b97877635e35b59dc30ec3b1a 100644
--- a/tests/compiler/dart2js/assert_message_throw_test.dart
+++ b/tests/compiler/dart2js/assert_message_throw_test.dart
@@ -63,7 +63,8 @@ main() {
         compiler.resolutionWorldBuilder.closedWorldForTesting;
 
     void check(String methodName, TypeMask expectedReturnType) {
-      MemberElement element = compiler.mainApp.find(methodName);
+      LibraryElement mainApp = compiler.mainApp;
+      MemberElement element = mainApp.find(methodName);
       TypeMask typeMask = simplify(
           compiler.globalInference.results.resultOfMember(element).returnType,
           closedWorld);