Standardize usage of virtual/override/final in extensions/

extensions/browser/extension_pref_store.h

Index: extensions/browser/extension_pref_store.h
diff --git a/extensions/browser/extension_pref_store.h b/extensions/browser/extension_pref_store.h
index 0d5824d71b5cfdceb1f5011b69646f58e6ccfc2f..162033c924a1564f4077689e5b9334746b4a0b1a 100644
--- a/extensions/browser/extension_pref_store.h
+++ b/extensions/browser/extension_pref_store.h
@@ -21,12 +21,12 @@ class ExtensionPrefStore : public ValueMapPrefStore,
                      bool incognito_pref_store);
 
   // Overrides for ExtensionPrefValueMap::Observer:
-  virtual void OnInitializationCompleted() override;
-  virtual void OnPrefValueChanged(const std::string& key) override;
-  virtual void OnExtensionPrefValueMapDestruction() override;
+  void OnInitializationCompleted() override;
+  void OnPrefValueChanged(const std::string& key) override;
+  void OnExtensionPrefValueMapDestruction() override;
 
  protected:
-  virtual ~ExtensionPrefStore();
+  ~ExtensionPrefStore() override;
 
  private:
   ExtensionPrefValueMap* extension_pref_value_map_;  // Weak pointer.