Standardize usage of virtual/override/final in content/browser/

content/browser/notification_service_impl.h

Index: content/browser/notification_service_impl.h
diff --git a/content/browser/notification_service_impl.h b/content/browser/notification_service_impl.h
index 7d0ecaa72e58823cc3f1cbd72a123ea1e58fbcc6..2df369a6d0ffad2a7f723efceb60b4c5c7f56c78 100644
--- a/content/browser/notification_service_impl.h
+++ b/content/browser/notification_service_impl.h
@@ -23,12 +23,12 @@ class CONTENT_EXPORT NotificationServiceImpl : public NotificationService {
   // Normally instantiated when the thread is created.  Not all threads have
   // a NotificationService.  Only one instance should be created per thread.
   NotificationServiceImpl();
-  virtual ~NotificationServiceImpl();
+  ~NotificationServiceImpl() override;
 
   // NotificationService:
-  virtual void Notify(int type,
-                      const NotificationSource& source,
-                      const NotificationDetails& details) override;
+  void Notify(int type,
+              const NotificationSource& source,
+              const NotificationDetails& details) override;
 
  private:
   friend class NotificationRegistrar;