replace platform conditions with os_posix and os_bsd where applicable

third_party/expat/expat.gyp

 # Copyright (c) 2011 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.
 
 {
   'target_defaults': {
     'defines': [
       '_LIB',
       'XML_STATIC',  # Compile for static linkage.
     ],
@@ skipping 41 matching lines @@
             'defines': [
               'XML_STATIC',  # Tell dependants to expect static linkage.
             ],
           },
           'conditions': [
             ['OS=="win"', {
               'defines': [
                 'COMPILED_FROM_DSP',
               ],
             }],
-            ['OS=="mac" or OS=="android" or OS=="freebsd" or OS=="openbsd"', {
+            ['OS=="mac" or OS=="android" or os_bsd==1', {
               'defines': [
                 'HAVE_EXPAT_CONFIG_H',
               ],
             }],
           ],
         },
       ],
     }],
   ],
 }