Fix warnings_checker.dart handling of multitests

tests/language_strong/generic_methods_bounds_test.dart

 // Copyright (c) 2017, 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 that a dynamic call to a generic function checks the type argument
 // against its bound.
 
 library generic_methods_bounds_test;
 
 import "package:expect/expect.dart";
 
 class A {}
 
 class B {}
 
 class C {
   void fun<T extends A>(T t) {}
 }
 
 main() {
   C c = new C();
-  c.fun<B>(new B()); /// 01: compile-time error
+  c.fun<B>(new B()); //# 01: compile-time error
 
   dynamic obj = new C();
-  obj.fun<B>(new B()); /// 02: runtime error
+  obj.fun<B>(new B()); //# 02: runtime error
 }