[SyncFS] Use nullptr instead of NULL

chrome/browser/sync_file_system/local/local_file_change_tracker.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/local/local_file_change_tracker.h"
 
 #include <queue>
 
 #include "base/location.h"
 #include "base/logging.h"
@@ skipping 397 matching lines @@
   }
   return SYNC_STATUS_OK;
 }
 
 void LocalFileChangeTracker::RecordChange(
     const FileSystemURL& url, const FileChange& change) {
   DCHECK(file_task_runner_->RunsTasksOnCurrentThread());
   int change_seq = current_change_seq_number_++;
   if (ContainsKey(demoted_changes_, url)) {
     RecordChangeToChangeMaps(url, change, change_seq,
-                             &demoted_changes_, NULL);
+                             &demoted_changes_, nullptr);
   } else {
     RecordChangeToChangeMaps(url, change, change_seq, &changes_, &change_seqs_);
   }
-  if (ContainsKey(mirror_changes_, url))
-    RecordChangeToChangeMaps(url, change, change_seq, &mirror_changes_, NULL);
+  if (ContainsKey(mirror_changes_, url)) {
+    RecordChangeToChangeMaps(url, change, change_seq, &mirror_changes_,
+                             nullptr);
+  }
   UpdateNumChanges();
 }
 
 // static
 void LocalFileChangeTracker::RecordChangeToChangeMaps(
     const FileSystemURL& url,
     const FileChange& change,
     int new_change_seq,
     FileChangeMap* changes,
     ChangeSeqMap* change_seqs) {
@@ skipping 173 matching lines @@
   if (!status.ok() && !status.IsNotFound()) {
     HandleError(FROM_HERE, status);
     db_status_ = LevelDBStatusToSyncStatusCode(status);
     db_.reset();
     return db_status_;
   }
   return SYNC_STATUS_OK;
 }
 
 }  // namespace sync_file_system