Extract locking behaviour from ProcessSingleton.

chrome/browser/process_singleton_mac.cc

 // 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 <errno.h>
 #include <fcntl.h>
 #include <sys/file.h>
 
 #include "chrome/browser/process_singleton.h"
 
@@ skipping 23 matching lines @@
 //
 // Neither of those cases apply on the Mac. Launch Services ensures that there
 // is only one instance of the process, and we get URLs to open via AppleEvents
 // and, once again, the Launch Services system. We have no need to manage this
 // ourselves.  An exclusive lock is used to flush out anyone making incorrect
 // assumptions.
 
 ProcessSingleton::ProcessSingleton(
     const base::FilePath& user_data_dir,
     const NotificationCallback& /* notification_callback */)
-    : locked_(false),
-      foreground_window_(NULL),
+    : foreground_window_(NULL),
       lock_path_(user_data_dir.Append(chrome::kSingletonLockFilename)),
       lock_fd_(-1) {
 }
 
 ProcessSingleton::~ProcessSingleton() {
   // Make sure the lock is released.  Process death will also release
   // it, even if this is not called.
   Cleanup();
 }
 
@@ skipping 55 matching lines @@
 }
 
 void ProcessSingleton::Cleanup() {
   // Closing the file also releases the lock.
   if (lock_fd_ != -1) {
     int rc = HANDLE_EINTR(close(lock_fd_));
     DPCHECK(!rc) << "Closing lock_fd_:";
   }
   lock_fd_ = -1;
 }