This adds adds four macros when compiling using GTEST_OS_MAC:

testing/gtest.gyp

 # Copyright (c) 2009 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': [
     {
       'target_name': 'gtest',
       'type': '<(library)',
       'msvs_guid': 'BFE8E2A7-3B3B-43B0-A994-3058B852DB8B',
@@ skipping 33 matching lines @@
       'sources!': [
         'gtest/src/gtest-all.cc',  # Not needed by our build.
       ],
       'include_dirs': [
         'gtest',
         'gtest/include',
       ],
       'conditions': [
         ['OS == "mac"', {
           'sources': [
+            'gtest_mac.h',
+            'gtest_mac.mm',
             'platform_test_mac.mm'
           ],
           'link_settings': {
             'libraries': [
               '$(SDKROOT)/System/Library/Frameworks/Foundation.framework',
             ],
           },
         }],
         ['OS == "mac" or OS == "linux" or OS == "freebsd" or OS == "openbsd"', {
           'defines': [
@@ skipping 39 matching lines @@
       ],
     },
   ],
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: