Fix warnings_checker.dart handling of multitests

tests/language/static_final_field2_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.
 // Disallow re-assignment of a final static variable.
 
 class A {
   static const x = 1;
 }
 
 class B {
   const B() : n = 5;
   final n;
-  static const a; // /// 02: compile-time error
+  static const a; // //# 02: compile-time error
   static const b = 3 + 5;
 }
 
 main() {
-  A.x = 2; // /// 01: static type warning, runtime error
+  A.x = 2; // //# 01: static type warning, runtime error
   new B();
   print(B.b);
-  print(B.a); // /// 02: continued
+  print(B.a); // //# 02: continued
 }