Standardize usage of virtual/override/final in sync/

sync/test/null_directory_change_delegate.h

 // 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.
 
 #ifndef SYNC_TEST_NULL_DIRECTORY_CHANGE_DELEGATE_H_
 #define SYNC_TEST_NULL_DIRECTORY_CHANGE_DELEGATE_H_
 
 #include "base/compiler_specific.h"
 #include "sync/syncable/directory_change_delegate.h"
 
 namespace syncer {
 namespace syncable {
 
 // DirectoryChangeDelegate that does nothing in all delegate methods.
 class NullDirectoryChangeDelegate : public DirectoryChangeDelegate {
  public:
-  virtual ~NullDirectoryChangeDelegate();
+  ~NullDirectoryChangeDelegate() override;
 
-  virtual void HandleCalculateChangesChangeEventFromSyncApi(
+  void HandleCalculateChangesChangeEventFromSyncApi(
       const ImmutableWriteTransactionInfo& write_transaction_info,
       BaseTransaction* trans,
       std::vector<int64>* entries_changed) override;
-  virtual void HandleCalculateChangesChangeEventFromSyncer(
+  void HandleCalculateChangesChangeEventFromSyncer(
       const ImmutableWriteTransactionInfo& write_transaction_info,
       BaseTransaction* trans,
       std::vector<int64>* entries_changed) override;
-  virtual ModelTypeSet HandleTransactionEndingChangeEvent(
+  ModelTypeSet HandleTransactionEndingChangeEvent(
       const ImmutableWriteTransactionInfo& write_transaction_info,
       BaseTransaction* trans) override;
-  virtual void HandleTransactionCompleteChangeEvent(
+  void HandleTransactionCompleteChangeEvent(
       ModelTypeSet models_with_changes) override;
 };
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif  // SYNC_TEST_NULL_DIRECTORY_CHANGE_DELEGATE_H_