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

chrome/browser/chrome_browser_main.cc

Index: chrome/browser/chrome_browser_main.cc
diff --git a/chrome/browser/chrome_browser_main.cc b/chrome/browser/chrome_browser_main.cc
index cd0f028c0d3c3f961f6a7168a02013ed48f58c92..5a0e1f7832667b8ca0a447e8b2505d97da93bfea 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -509,12 +509,12 @@ class LoadCompleteListener : public content::NotificationObserver {
                    content::NOTIFICATION_LOAD_COMPLETED_MAIN_FRAME,
                    content::NotificationService::AllSources());
   }
-  virtual ~LoadCompleteListener() {}
+  ~LoadCompleteListener() override {}
 
   // content::NotificationObserver implementation.
-  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 {
     DCHECK_EQ(content::NOTIFICATION_LOAD_COMPLETED_MAIN_FRAME, type);
     startup_metric_utils::OnInitialPageLoadComplete();
     delete this;