Fix warnings_checker.dart handling of multitests

tests/language_strong/malbounded_type_test2_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.
 
 import "package:expect/expect.dart";
 
 isCheckedMode() {
   try {
     var i = 1;
     String s = i;
     return false;
   } catch (e) {
     return true;
   }
 }
 
 class A<T extends num> { }
 
 class B<T> {
   test() {
-    new A() is A<T>; // /// static type warning
+    new A() is A<T>; // //# static type warning
   }
 }
 
 main () {
   var b = new B<String>();
   if (isCheckedMode()) {
     Expect.throws(() => b.test(), (e) => e is TypeError);
   } else {
     b.test();
   }
 }