[SyncFS] Use nullptr instead of NULL

chrome/browser/sync_file_system/drive_backend/folder_creator.cc

 // Copyright 2013 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/sync_file_system/drive_backend/folder_creator.h"
 
 #include "chrome/browser/drive/drive_api_util.h"
 #include "chrome/browser/drive/drive_service_interface.h"
 #include "chrome/browser/sync_file_system/drive_backend/drive_backend_util.h"
 #include "chrome/browser/sync_file_system/drive_backend/metadata_database.h"
@@ skipping 78 matching lines @@
 
   if (!file_list->next_link().is_empty()) {
     drive_service_->GetRemainingFileList(
         file_list->next_link(),
         base::Bind(&FolderCreator::DidListFolders,
                    weak_ptr_factory_.GetWeakPtr(), callback,
                    base::Passed(&candidates)));
     return;
   }
 
-  const google_apis::FileResource* oldest = NULL;
+  const google_apis::FileResource* oldest = nullptr;
   for (size_t i = 0; i < candidates.size(); ++i) {
     const google_apis::FileResource& entry = *candidates[i];
     if (!entry.IsDirectory() || entry.labels().is_trashed())
       continue;
 
     if (!oldest || oldest->created_date() > entry.created_date())
       oldest = &entry;
   }
 
   if (!oldest) {
     callback.Run(std::string(), SYNC_FILE_ERROR_NOT_FOUND);
     return;
   }
 
   std::string file_id = oldest->file_id();
 
   status = metadata_database_->UpdateByFileResourceList(candidates.Pass());
   if (status != SYNC_STATUS_OK) {
     callback.Run(std::string(), status);
     return;
   }
 
   DCHECK(!file_id.empty());
-  if (!metadata_database_->FindFileByFileID(file_id, NULL)) {
+  if (!metadata_database_->FindFileByFileID(file_id, nullptr)) {
     callback.Run(std::string(), SYNC_FILE_ERROR_NOT_FOUND);
     return;
   }
 
   callback.Run(file_id, status);
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system