Standardize usage of virtual/override/final in extensions/

extensions/browser/extension_registry.h

Index: extensions/browser/extension_registry.h
diff --git a/extensions/browser/extension_registry.h b/extensions/browser/extension_registry.h
index 9221a77bb7b6c8bc3856f6aea0fc52d68738bcd5..50f75c9b7cdb42e45cc3c14457e086d02c493345 100644
--- a/extensions/browser/extension_registry.h
+++ b/extensions/browser/extension_registry.h
@@ -42,7 +42,7 @@ class ExtensionRegistry : public KeyedService {
   };
 
   explicit ExtensionRegistry(content::BrowserContext* browser_context);
-  virtual ~ExtensionRegistry();
+  ~ExtensionRegistry() override;
 
   // Returns the instance for the given |browser_context|.
   static ExtensionRegistry* Get(content::BrowserContext* browser_context);
@@ -146,7 +146,7 @@ class ExtensionRegistry : public KeyedService {
       const ExtensionSet::ModificationCallback& callback);
 
   // KeyedService implementation:
-  virtual void Shutdown() override;
+  void Shutdown() override;
 
  private:
   // Extensions that are installed, enabled and not terminated.