Standardize usage of virtual/override/final in extensions/

extensions/browser/event_router_unittest.cc

Index: extensions/browser/event_router_unittest.cc
diff --git a/extensions/browser/event_router_unittest.cc b/extensions/browser/event_router_unittest.cc
index fd45366e549324579e550fd6bf01646baa1a366f..007ca7ad428d91ad4f05eed740b9b7afac81505c 100644
--- a/extensions/browser/event_router_unittest.cc
+++ b/extensions/browser/event_router_unittest.cc
@@ -38,12 +38,12 @@ class MockEventRouterObserver : public EventRouter::Observer {
   }
 
   // EventRouter::Observer overrides:
-  virtual void OnListenerAdded(const EventListenerInfo& details) override {
+  void OnListenerAdded(const EventListenerInfo& details) override {
     listener_added_count_++;
     last_event_name_ = details.event_name;
   }
 
-  virtual void OnListenerRemoved(const EventListenerInfo& details) override {
+  void OnListenerRemoved(const EventListenerInfo& details) override {
     listener_removed_count_++;
     last_event_name_ = details.event_name;
   }