Progressively refacto FirstRun class to first_run namespace(part 4).

chrome/browser/first_run/first_run_mac.mm

 // Copyright (c) 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.
 
 #include "chrome/browser/first_run/first_run.h"
 
 #include "base/file_path.h"
 #include "base/string_util.h"
 #include "chrome/browser/first_run/first_run_internal.h"
 #include "chrome/browser/importer/importer_host.h"
@@ skipping 43 matching lines @@
                                      import_items,
                                      dont_import_items,
                                      search_engine_experiment,
                                      randomize_search_engine_experiment,
                                      make_chrome_default);
 
   process_singleton->Unlock();
   first_run::CreateSentinel();
 }
 
-}  //namespace first_run
-
-// static
-FilePath FirstRun::MasterPrefsPath() {
+FilePath MasterPrefsPath() {
   return master_prefs::MasterPrefsPath();
 }
+
+}  //namespace first_run