Add a GN flag for the Windows multi-dll build.

chrome/policy.gypi

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'targets': [
     {
+      # GN version: //chrome/browser/policy:path_parser
       'target_name': 'policy_path_parser',
       'type': 'static_library',
       'dependencies': [
         '../base/base.gyp:base',
         '../chrome/common_constants.gyp:common_constants',
         '../components/components.gyp:policy',
       ],
       'include_dirs': [
         '..',
       ],
       'sources': [
         'browser/policy/policy_path_parser.h',
         'browser/policy/policy_path_parser_linux.cc',
         'browser/policy/policy_path_parser_mac.mm',
         'browser/policy/policy_path_parser_win.cc',
       ],
     },
   ],
 }