Fix warnings_checker.dart handling of multitests

tests/language_strong/field_override4_test.dart

 // Copyright (c) 2013, 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 we report a compile-time error when an instance field conflicts
 // with an inherited instance method of the same name.
 
 import "package:expect/expect.dart";
 
 class A {
-  var foo = 42; // /// 00: ok
-  get foo => 42; // /// 01: ok
-  foo() => 42; // /// 02: compile-time error
-  set foo(value) { } // /// 03: ok
+  var foo = 42; // //# 00: ok
+  get foo => 42; // //# 01: ok
+  foo() => 42; // //# 02: compile-time error
+  set foo(value) { } // //# 03: ok
 }
 
 class B extends A {
   dynamic foo = 42;
 }
 
 main() {
   Expect.equals(42, new B().foo);
 }