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

chrome/browser/apps/app_shim/app_shim_handler_mac.cc

Index: chrome/browser/apps/app_shim/app_shim_handler_mac.cc
diff --git a/chrome/browser/apps/app_shim/app_shim_handler_mac.cc b/chrome/browser/apps/app_shim/app_shim_handler_mac.cc
index 5e6dcaea341c8ff0e4c10f642f0814207de6b074..e3bebd85fe9498994ba5e363799bc8ad743cc39a 100644
--- a/chrome/browser/apps/app_shim/app_shim_handler_mac.cc
+++ b/chrome/browser/apps/app_shim/app_shim_handler_mac.cc
@@ -91,13 +91,12 @@ class AppShimHandlerRegistry : public content::NotificationObserver {
         content::NotificationService::AllBrowserContextsAndSources());
   }
 
-  virtual ~AppShimHandlerRegistry() {}
+  ~AppShimHandlerRegistry() override {}
 
   // content::NotificationObserver override:
-  virtual void Observe(
-      int type,
-      const content::NotificationSource& source,
-      const content::NotificationDetails& details) override {
+  void Observe(int type,
+               const content::NotificationSource& source,
+               const content::NotificationDetails& details) override {
     switch (type) {
       case chrome::NOTIFICATION_BROWSER_OPENED:
       case chrome::NOTIFICATION_BROWSER_CLOSE_CANCELLED: