Re-arrange tests to allow testing generated messages code in dart2js

pkg/intl/test/message_extraction/generated_messages_js_test.dart

+// Copyright (c) 2013, 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.
+
+// This test is intended to be run when compiled to Javascript, though it will
+// also work if run from the VM, it just won't test anything different from
+// message_extraction_test. It runs the generated code without going through
+// the message extraction or translation, which can't be done in JS. This tells
+// us if the generated code works in JS.
+
+library generated_messages_js_test.dart;
+
+import 'package:unittest/unittest.dart';
+import 'sample_with_messages.dart' as sample;
+import 'print_to_list.dart';
+import 'verify_messages.dart';
+
+main() {
+  test("Test generated code running in JS", () =>
+    sample.main().then((_) => verifyResult(lines)));
+}