Use process_singleton_linux on Mac.

chrome/chrome_browser.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': [
     {
       'target_name': 'browser',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
@@ skipping 1721 matching lines @@
         'browser/printing/printer_manager_dialog_win.cc',
         'browser/printing/printer_query.cc',
         'browser/printing/printer_query.h',
         'browser/printing/printing_message_filter.cc',
         'browser/printing/printing_message_filter.h',
         'browser/printing/printing_ui_web_contents_observer.cc',
         'browser/printing/printing_ui_web_contents_observer.h',
         'browser/process_info_snapshot.h',
         'browser/process_info_snapshot_mac.cc',
         'browser/process_singleton.h',
-        'browser/process_singleton_linux.cc',
-        'browser/process_singleton_mac.cc',
+        'browser/process_singleton_posix.cc',
         'browser/process_singleton_modal_dialog_lock.cc',
         'browser/process_singleton_modal_dialog_lock.h',
         'browser/process_singleton_startup_lock.cc',
         'browser/process_singleton_startup_lock.h',
         'browser/process_singleton_win.cc',
         'browser/profile_resetter/automatic_profile_resetter.h',
         'browser/profile_resetter/automatic_profile_resetter.cc',
         'browser/profile_resetter/automatic_profile_resetter_delegate.h',
         'browser/profile_resetter/automatic_profile_resetter_delegate.cc',
         'browser/profile_resetter/automatic_profile_resetter_factory.h',
@@ skipping 1580 matching lines @@
             'browser/idle_android.cc',
             'browser/idle.cc',
             'browser/lifetime/application_lifetime_stub.cc',
             'browser/lifetime/browser_close_manager.cc',
             'browser/net/predictor_tab_helper.cc',
             'browser/parsers/metadata_parser_jpeg.cc',
             'browser/parsers/metadata_parser_jpeg_factory.cc',
             'browser/parsers/metadata_parser_manager.cc',
             'browser/process_singleton.cc',
             'browser/process_singleton_modal_dialog_lock.cc',
+            'browser/process_singleton_posix.cc',
             'browser/process_singleton_startup_lock.cc',
             'browser/profiles/profile_shortcut_manager.cc',
             'browser/repost_form_warning_controller.cc',
             'browser/search/search_terms_tracker.cc',
             'browser/sessions/session_command.cc',
             'browser/speech/extension_api/tts_extension_api_constants.cc',
             'browser/ssl/ssl_add_cert_handler.cc',
             'browser/ssl/ssl_client_auth_observer.cc',
             'browser/status_icons/desktop_notification_balloon.cc',
             'browser/signin/signin_ui_util.cc',
@@ skipping 488 matching lines @@
             'package_name': 'org/chromium/chrome/browser',
             'template_deps': ['browser/android/tab_load_status.h'],
           },
           'includes': [ '../build/android/java_cpp_template.gypi' ],
         },
       ],
      },
     ],
   ],
 }