Standardize usage of virtual/override/final in chrome/browser/sync/

chrome/browser/sync/glue/history_model_worker.h

Index: chrome/browser/sync/glue/history_model_worker.h
diff --git a/chrome/browser/sync/glue/history_model_worker.h b/chrome/browser/sync/glue/history_model_worker.h
index 241fc32dd3398cf2abcfbdc65c17a32105fc6c24..1d73e5193c539b4bd19d560b4fd3ec2e586507f6 100644
--- a/chrome/browser/sync/glue/history_model_worker.h
+++ b/chrome/browser/sync/glue/history_model_worker.h
@@ -29,19 +29,19 @@ class HistoryModelWorker : public syncer::ModelSafeWorker {
       syncer::WorkerLoopDestructionObserver* observer);
 
   // syncer::ModelSafeWorker implementation. Called on syncapi SyncerThread.
-  virtual void RegisterForLoopDestruction() override;
-  virtual syncer::ModelSafeGroup GetModelSafeGroup() override;
+  void RegisterForLoopDestruction() override;
+  syncer::ModelSafeGroup GetModelSafeGroup() override;
 
   // Called on history DB thread to register HistoryModelWorker to observe
   // destruction of history backend loop.
   void RegisterOnDBThread();
 
  protected:
-  virtual syncer::SyncerError DoWorkAndWaitUntilDoneImpl(
+  syncer::SyncerError DoWorkAndWaitUntilDoneImpl(
       const syncer::WorkCallback& work) override;
 
  private:
-  virtual ~HistoryModelWorker();
+  ~HistoryModelWorker() override;
 
   const base::WeakPtr<HistoryService> history_service_;
   // Helper object to make sure we don't leave tasks running on the history