Fix warnings_checker.dart handling of multitests

tests/lib/mirrors/symbol_validation_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.
 
 library symbol_validation_test;
 
 import 'dart:mirrors';
 import 'package:expect/expect.dart';
 
 validSymbol(String string) {
@@ skipping 115 matching lines @@
     "typedef"
   ];
   builtInIdentifiers.expand((w) => [w, "$w=", "x.$w" , "$w.x", "x.$w.x",
                                     "$w=", "x.$w="])
                     .forEach(validSymbol);
 
   var privateSymbols = [
     '_', '_x', 'x._y', 'x._', 'x.y._', 'x._.y', '_true'
   ];
   privateSymbols.forEach(invalidSymbol);
-  privateSymbols.forEach(validPrivateSymbol); //  /// 01: ok
+  privateSymbols.forEach(validPrivateSymbol); //  //# 01: ok
 }