Use process_singleton_linux on Mac.

chrome/chrome_tests_unit.gypi

 # Copyright 2012 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': [
     {
       # This target contains mocks and test utilities that don't belong in
       # production libraries but are used by more than one test executable.
       'target_name': 'test_support_common',
       'type': 'static_library',
@@ skipping 1156 matching lines @@
         'browser/prerender/prerender_tracker_unittest.cc',
         'browser/prerender/prerender_unittest.cc',
         'browser/prerender/prerender_util_unittest.cc',
         'browser/printing/cloud_print/cloud_print_proxy_service_unittest.cc',
         'browser/printing/print_dialog_cloud_unittest.cc',
         'browser/printing/print_job_unittest.cc',
         'browser/printing/print_preview_dialog_controller_unittest.cc',
         'browser/printing/print_preview_test.cc',
         'browser/printing/print_preview_test.h',
         'browser/process_info_snapshot_mac_unittest.cc',
-        'browser/process_singleton_linux_unittest.cc',
-        'browser/process_singleton_mac_unittest.cc',
+        'browser/process_singleton_posix_unittest.cc',
         'browser/profile_resetter/automatic_profile_resetter_delegate_unittest.cc',
         'browser/profile_resetter/automatic_profile_resetter_unittest.cc',
         'browser/profile_resetter/jtl_interpreter_unittest.cc',
         'browser/profile_resetter/profile_resetter_unittest.cc',
         'browser/profiles/file_path_verifier_win_unittest.cc',
         'browser/profiles/gaia_info_update_service_unittest.cc',
         'browser/profiles/incognito_mode_policy_handler_unittest.cc',
         'browser/profiles/off_the_record_profile_impl_unittest.cc',
         'browser/profiles/profile_downloader_unittest.cc',
         'browser/profiles/profile_info_cache_unittest.cc',
@@ skipping 1288 matching lines @@
 
             # Sync setup uses native ui.
             'browser/ui/webui/sync_setup_handler_unittest.cc',
             'browser/sync/sync_ui_util_unittest.cc',
 
             'browser/browser_commands_unittest.cc',
             'browser/download/download_shelf_unittest.cc',
             'browser/extensions/extension_message_bubble_controller_unittest.cc',
             'browser/extensions/extension_test_message_listener_unittest.cc',
             'browser/policy/policy_path_parser_unittest.cc',
+            'browser/process_singleton_posix_unittest.cc',
             'browser/profiles/off_the_record_profile_impl_unittest.cc',
             'browser/profiles/profile_list_desktop_unittest.cc',
             'browser/renderer_context_menu/render_view_context_menu_unittest.cc',
             'browser/search/instant_service_unittest.cc',
             'browser/search/search_unittest.cc',
             'browser/sync/sessions/sessions_sync_manager_unittest.cc',
             'browser/sync/sync_global_error_unittest.cc',
             'browser/translate/translate_manager_render_view_host_unittest.cc',
             'browser/ui/browser_instant_controller_unittest.cc',
             'browser/ui/bookmarks/bookmark_bubble_sign_in_delegate_unittest.cc',
@@ skipping 356 matching lines @@
             'browser/ui/app_list/test/fake_profile_store.h',
             'browser/ui/app_list/test/fast_show_pickler_unittest.cc',
             'browser/ui/views/app_list/linux/app_list_linux_unittest.cc',
             'browser/ui/views/app_list/win/app_list_win_unittest.cc',
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }