Standardize usage of virtual/override/final in sync/

sync/syncable/syncable_model_neutral_write_transaction.h

Index: sync/syncable/syncable_model_neutral_write_transaction.h
diff --git a/sync/syncable/syncable_model_neutral_write_transaction.h b/sync/syncable/syncable_model_neutral_write_transaction.h
index 1ec3e939fc20c73bb8a980e867740b6448c47221..3caa10ea3fb28398ea7a3c9ed31737d082fef200 100644
--- a/sync/syncable/syncable_model_neutral_write_transaction.h
+++ b/sync/syncable/syncable_model_neutral_write_transaction.h
@@ -28,9 +28,9 @@ class SYNC_EXPORT_PRIVATE ModelNeutralWriteTransaction
       const tracked_objects::Location& location,
       WriterTag writer,
       Directory* directory);
-  virtual ~ModelNeutralWriteTransaction();
+  ~ModelNeutralWriteTransaction() override;
 
-  virtual void TrackChangesTo(const EntryKernel* entry) override;
+  void TrackChangesTo(const EntryKernel* entry) override;
 
  private:
   MetahandleSet modified_handles_;