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

chrome/browser/sync_file_system/drive_backend/list_changes_task.h

Index: chrome/browser/sync_file_system/drive_backend/list_changes_task.h
diff --git a/chrome/browser/sync_file_system/drive_backend/list_changes_task.h b/chrome/browser/sync_file_system/drive_backend/list_changes_task.h
index 6c468a498c50d9429c4d7d18ec54f5bb8e8e7d7f..fb936295d92f32332cc051b5fe86ebaa3dd6e3f4 100644
--- a/chrome/browser/sync_file_system/drive_backend/list_changes_task.h
+++ b/chrome/browser/sync_file_system/drive_backend/list_changes_task.h
@@ -29,9 +29,9 @@ class SyncEngineContext;
 class ListChangesTask : public SyncTask {
  public:
   explicit ListChangesTask(SyncEngineContext* sync_context);
-  virtual ~ListChangesTask();
+  ~ListChangesTask() override;
 
-  virtual void RunPreflight(scoped_ptr<SyncTaskToken> token) override;
+  void RunPreflight(scoped_ptr<SyncTaskToken> token) override;
 
  private:
   void StartListing(scoped_ptr<SyncTaskToken> token);