Handle protocol buffer messages with no package

test/generated_message_test.dart

 #!/usr/bin/env 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.
 
 library generated_message_test;
 
 import 'package:protobuf/protobuf.dart';
 import 'package:unittest/unittest.dart';
 
 import '../out/protos/google/protobuf/unittest.pb.dart';
 import '../out/protos/google/protobuf/unittest_import.pb.dart';
 import '../out/protos/google/protobuf/unittest_optimize_for.pb.dart';
 import '../out/protos/multiple_files_test.pb.dart';
 import '../out/protos/nested_extension.pb.dart';
 import '../out/protos/non_nested_extension.pb.dart';
 import '../out/protos/reserved_names.pb.dart';
 import '../out/protos/duplicate_names_import.pb.dart';
 import '../out/protos/package1.pb.dart' as p1;
 import '../out/protos/package2.pb.dart' as p2;
 import '../out/protos/package3.pb.dart' as p3;
+import '../out/protos/toplevel_import.pb.dart' as t;
+import '../out/protos/toplevel.pb.dart';
 
 import 'test_util.dart';
 
 void main() {
   final throwsInvalidProtocolBufferException =
       throwsA(new isInstanceOf<InvalidProtocolBufferException>());
   test('testProtosShareRepeatedArraysIfDidntChange', () {
     TestAllTypes value1 = new TestAllTypes()
         ..repeatedInt32.add(100)
         ..repeatedImportEnum.add(ImportEnum.IMPORT_BAR)
@@ skipping 560 matching lines @@
 
   test('testImportDuplicatenames', () {
     M message = new M();
     message.m1 = new p1.M();
     message.m1M = new p1.M_M();
     message.m2 = new p2.M();
     message.m2M = new p2.M_M();
     message.m3 = new p3.M();
     message.m3M = new p3.M_M();
   });
+
+  test('testToplevel', () {
+    t.M message = new t.M();
+    message.t = new T();
+  });
 }