Fix warnings_checker.dart handling of multitests

tests/language_strong/unresolved_default_constructor_test.dart

 // Copyright (c) 2014, 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.
 
 // Test unresolved default constructor calls remain unresolved after dart2dart
 // translation.
 
 import 'package:expect/expect.dart';
 
 class A {
   A.named();
   static method() {}
 }
 
 main() {
   A.method();
-  Expect.throws(() => new A()); /// 01: static type warning
+  Expect.throws(() => new A()); //# 01: static type warning
 }