Standardize usage of virtual/override/final in extensions/

extensions/browser/api/app_window/app_window_apitest.cc

Index: extensions/browser/api/app_window/app_window_apitest.cc
diff --git a/extensions/browser/api/app_window/app_window_apitest.cc b/extensions/browser/api/app_window/app_window_apitest.cc
index 644ba5dcd8e0565348b7d74046805af38a0e46b7..1e60760501eb4855187d6b905413e2df617f25fd 100644
--- a/extensions/browser/api/app_window/app_window_apitest.cc
+++ b/extensions/browser/api/app_window/app_window_apitest.cc
@@ -29,12 +29,12 @@ class TestAppWindowRegistryObserver : public AppWindowRegistry::Observer {
       : profile_(profile), icon_updates_(0) {
     AppWindowRegistry::Get(profile_)->AddObserver(this);
   }
-  virtual ~TestAppWindowRegistryObserver() {
+  ~TestAppWindowRegistryObserver() override {
     AppWindowRegistry::Get(profile_)->RemoveObserver(this);
   }
 
   // Overridden from AppWindowRegistry::Observer:
-  virtual void OnAppWindowIconChanged(AppWindow* app_window) override {
+  void OnAppWindowIconChanged(AppWindow* app_window) override {
     ++icon_updates_;
   }