Standardize usage of virtual/override/final in extensions/

extensions/browser/extension_web_contents_observer.h

Index: extensions/browser/extension_web_contents_observer.h
diff --git a/extensions/browser/extension_web_contents_observer.h b/extensions/browser/extension_web_contents_observer.h
index 74cc5548f9bf2a2d64ecb91ce7cb3cdf975220e5..cd5712c18d94a2abf12e65c795c01c0dd7de5f6a 100644
--- a/extensions/browser/extension_web_contents_observer.h
+++ b/extensions/browser/extension_web_contents_observer.h
@@ -31,15 +31,14 @@ class Extension;
 class ExtensionWebContentsObserver : public content::WebContentsObserver {
  protected:
   explicit ExtensionWebContentsObserver(content::WebContents* web_contents);
-  virtual ~ExtensionWebContentsObserver();
+  ~ExtensionWebContentsObserver() override;
 
   content::BrowserContext* browser_context() { return browser_context_; }
 
   // content::WebContentsObserver overrides.
 
   // A subclass should invoke this method to finish extension process setup.
-  virtual void RenderViewCreated(content::RenderViewHost* render_view_host)
-      override;
+  void RenderViewCreated(content::RenderViewHost* render_view_host) override;
 
   // Returns the extension or app associated with a render view host. Returns
   // NULL if the render view host is not for a valid extension.