Fix warnings_checker.dart handling of multitests

tests/language_strong/class_cycle_test.dart

 // Copyright (c) 2012, 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 fail because of cycles in super class relationship.
 
 import "package:expect/expect.dart";
 
 class Foo implements Bar {
 }
 
 class C {
 }
 
 class Bar
-    extends Foo // /// 00: compile-time error
-    implements Foo // /// 01: compile-time error
+    extends Foo // //# 00: compile-time error
+    implements Foo // //# 01: compile-time error
 {
 }
 
 class ImplementsC implements C
-, C // /// 02: compile-time error
+, C // //# 02: compile-time error
 {}
 
 // Spec says: It is a compile-time error if the superclass
 // of a class C appears in the implements clause of C.
 class ExtendsC extends C
-implements C // /// 03: compile-time error
+implements C // //# 03: compile-time error
 {}
 
 main() {
   Expect.isTrue(new Foo() is Foo);
   Expect.isTrue(new ImplementsC() is C);
   Expect.isTrue(new ExtendsC() is C);
 }