[SyncFS] Use nullptr instead of NULL

chrome/browser/sync_file_system/drive_backend/metadata_database_index.cc

 // 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.
 
 #include "chrome/browser/sync_file_system/drive_backend/metadata_database_index.h"
 
 #include "base/metrics/histogram.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/threading/thread_restrictions.h"
@@ skipping 152 matching lines @@
         LookUpMap(trackers_by_parent, tracker_id, std::set<int64>()),
         &pending);
   }
 
   // Delete all unreachable trackers.
   ScopedVector<FileTracker> reachable_trackers;
   for (size_t i = 0; i < contents->file_trackers.size(); ++i) {
     FileTracker* tracker = contents->file_trackers[i];
     if (ContainsKey(visited_trackers, tracker->tracker_id())) {
       reachable_trackers.push_back(tracker);
-      contents->file_trackers[i] = NULL;
+      contents->file_trackers[i] = nullptr;
     } else {
       PutFileTrackerDeletionToDB(tracker->tracker_id(), db);
     }
   }
   contents->file_trackers = reachable_trackers.Pass();
 
   // List all |file_id| referred by a tracker.
   base::hash_set<std::string> referred_file_ids;
   for (size_t i = 0; i < contents->file_trackers.size(); ++i)
     referred_file_ids.insert(contents->file_trackers[i]->file_id());
 
   // Delete all unreferred metadata.
   ScopedVector<FileMetadata> referred_file_metadata;
   for (size_t i = 0; i < contents->file_metadata.size(); ++i) {
     FileMetadata* metadata = contents->file_metadata[i];
     if (ContainsKey(referred_file_ids, metadata->file_id())) {
       referred_file_metadata.push_back(metadata);
-      contents->file_metadata[i] = NULL;
+      contents->file_metadata[i] = nullptr;
     } else {
       PutFileMetadataDeletionToDB(metadata->file_id(), db);
     }
   }
   contents->file_metadata = referred_file_metadata.Pass();
 }
 
 }  // namespace
 
 // static
@@ skipping 541 matching lines @@
 
     DVLOG(3) << "  Remove from dirty_trackers_: " << tracker_id;
     dirty_trackers_.erase(tracker_id);
 
     demoted_dirty_trackers_.erase(tracker_id);
   }
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system