Standardize usage of virtual/override/final in extensions/

extensions/renderer/extension_helper.cc

Index: extensions/renderer/extension_helper.cc
diff --git a/extensions/renderer/extension_helper.cc b/extensions/renderer/extension_helper.cc
index 3e8018bd37ca9c910323482a57f35a0c0bfc6bed..f12b526e2d95de3764af5a8044b94c728f4990ae 100644
--- a/extensions/renderer/extension_helper.cc
+++ b/extensions/renderer/extension_helper.cc
@@ -47,7 +47,7 @@ class ViewAccumulator : public content::RenderViewVisitor {
   std::vector<content::RenderView*> views() { return views_; }
 
   // Returns false to terminate the iteration.
-  virtual bool Visit(content::RenderView* render_view) override {
+  bool Visit(content::RenderView* render_view) override {
     ExtensionHelper* helper = ExtensionHelper::Get(render_view);
     if (!ViewTypeMatches(helper->view_type(), view_type_))
       return true;