Standardize usage of virtual/override/final in extensions/

extensions/browser/extension_function_dispatcher.cc

Index: extensions/browser/extension_function_dispatcher.cc
diff --git a/extensions/browser/extension_function_dispatcher.cc b/extensions/browser/extension_function_dispatcher.cc
index b4924b21fca6994cbf367a2ec6bd1c8d6638d188..f9bbec561b911df0eadb21606c01769ed0b4916f 100644
--- a/extensions/browser/extension_function_dispatcher.cc
+++ b/extensions/browser/extension_function_dispatcher.cc
@@ -152,12 +152,10 @@ class ExtensionFunctionDispatcher::UIThreadResponseCallbackWrapper
         weak_ptr_factory_(this) {
   }
 
-  virtual ~UIThreadResponseCallbackWrapper() {
-  }
+  ~UIThreadResponseCallbackWrapper() override {}
 
   // content::WebContentsObserver overrides.
-  virtual void RenderViewDeleted(
-      RenderViewHost* render_view_host) override {
+  void RenderViewDeleted(RenderViewHost* render_view_host) override {
     DCHECK_CURRENTLY_ON(BrowserThread::UI);
     if (render_view_host != render_view_host_)
       return;