[Sync] Replacing NULL with nullptr in code and null in comments for components/sync/

components/sync/engine_impl/syncer_proto_util.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 "components/sync/engine_impl/syncer_proto_util.h"
 
 #include <map>
 
 #include "base/format_macros.h"
 #include "base/strings/stringprintf.h"
@@ skipping 480 matching lines @@
       return SERVER_RETURN_NOT_MY_BIRTHDAY;
     case DISABLED_BY_ADMIN:
       return SERVER_RETURN_DISABLED_BY_ADMIN;
     case PARTIAL_FAILURE:
       // This only happens when partial throttling during GetUpdates.
       if (!sync_protocol_error.error_data_types.Empty()) {
         DLOG(WARNING) << "Some types throttled by syncer during GetUpdates.";
         cycle->delegate()->OnTypesThrottled(
             sync_protocol_error.error_data_types, GetThrottleDelay(*response));
       }
-      if (partial_failure_data_types != NULL) {
+      if (partial_failure_data_types != nullptr) {
         *partial_failure_data_types = sync_protocol_error.error_data_types;
       }
       return SERVER_RETURN_PARTIAL_FAILURE;
     case CLIENT_DATA_OBSOLETE:
       return SERVER_RETURN_CLIENT_DATA_OBSOLETE;
     default:
       NOTREACHED();
       return UNSET;
   }
 }
@@ skipping 82 matching lines @@
 std::string SyncerProtoUtil::ClientToServerResponseDebugString(
     const ClientToServerResponse& response) {
   // Add more handlers as needed.
   std::string output;
   if (response.has_get_updates())
     output.append(GetUpdatesResponseString(response.get_updates()));
   return output;
 }
 
 }  // namespace syncer