Fix warnings_checker.dart handling of multitests

tests/language/bool_condition_check_test.dart

 // Copyright (c) 2015, 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.
 
 // Check that passing `null` for a boolean typed parameter will still cause
 // a boolean conversion error when used in a condition in checked mode.
 
 import 'package:expect/expect.dart';
 
 @NoInline()
 String check({bool a, bool b}) {
   String a_string = a ? 'a' : '';
   String b_string = b ? 'b' : '';
   return '$a_string$b_string';
 }
 
 class Class {
   final String field;
   Class({bool a: false, bool b: true}) : this.field = check(a: a, b: b);
 }
 
 main() {
-  Expect.equals('', new Class(a: null, b: null).field); /// 01: dynamic type error
+  Expect.equals('', new Class(a: null, b: null).field); //# 01: dynamic type error
 }