[SyncFS] Use nullptr instead of NULL

chrome/browser/sync_file_system/drive_backend/sync_task_manager.h

 // Copyright 2014 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.
 
 #ifndef CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_SYNC_TASK_MANAGER_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_SYNC_TASK_MANAGER_H_
 
 #include <queue>
 #include <vector>
 
@@ skipping 145 matching lines @@
       const tracked_objects::Location& from_here,
       const SyncStatusCallback& callback,
       scoped_ptr<TaskBlocker> task_blocker);
 
   void PushPendingTask(const base::Closure& closure, Priority priority);
 
   void RunTask(scoped_ptr<SyncTaskToken> token,
                scoped_ptr<SyncTask> task);
 
   // Runs a pending task as a foreground task if possible.
-  // If |token| is non-NULL, put |token| back to |token_| beforehand.
+  // If |token| is non-nullptr, put |token| back to |token_| beforehand.
   void MaybeStartNextForegroundTask(scoped_ptr<SyncTaskToken> token);
 
   base::WeakPtr<Client> client_;
 
   // Owns running SyncTask to cancel the task on SyncTaskManager deletion.
   scoped_ptr<SyncTask> running_foreground_task_;
 
   // Owns running backgrounded SyncTask to cancel the task on SyncTaskManager
   // deletion.
   base::ScopedPtrHashMap<int64, SyncTask> running_background_tasks_;
@@ skipping 20 matching lines @@
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
   base::SequenceChecker sequence_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncTaskManager);
 };
 
 }  // namespace drive_backend
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_BACKEND_SYNC_TASK_MANAGER_H_