Fix warnings_checker.dart handling of multitests

tests/language/substring_test.dart

 // Copyright (c) 2011, 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.
 // Dart version of two-argument Ackermann-Peter function.
 
 import "package:expect/expect.dart";
 
 
 main() {
   try {
-    print("abcdef".substring(1.5, 3.5)); //   /// 01: static type warning
-    Expect.fail("Should have thrown an exception"); // /// 01: continued
+    print("abcdef".substring(1.5, 3.5)); //   //# 01: static type warning
+    Expect.fail("Should have thrown an exception"); // //# 01: continued
   } on TypeError catch (e) {
     // OK.
   } on ArgumentError catch (e) {
     // OK.
   }
 }