Update {virtual,override} to follow C++11 style in chrome.

chrome/renderer/prerender/prerender_dispatcher.h

Index: chrome/renderer/prerender/prerender_dispatcher.h
diff --git a/chrome/renderer/prerender/prerender_dispatcher.h b/chrome/renderer/prerender/prerender_dispatcher.h
index aa4b7cf4ea6556b2c52378fa443bed029164ee02..52038f10844e402991e809cf24e40a2a0aa5f613 100644
--- a/chrome/renderer/prerender/prerender_dispatcher.h
+++ b/chrome/renderer/prerender/prerender_dispatcher.h
@@ -27,7 +27,7 @@ class PrerenderDispatcher : public content::RenderProcessObserver,
                             public blink::WebPrerenderingSupport {
  public:
   PrerenderDispatcher();
-  virtual ~PrerenderDispatcher();
+  ~PrerenderDispatcher() override;
 
   bool IsPrerenderURL(const GURL& url) const;
 
@@ -46,9 +46,9 @@ class PrerenderDispatcher : public content::RenderProcessObserver,
   bool OnControlMessageReceived(const IPC::Message& message) override;
 
   // From WebPrerenderingSupport:
-  virtual void add(const blink::WebPrerender& prerender) override;
-  virtual void cancel(const blink::WebPrerender& prerender) override;
-  virtual void abandon(const blink::WebPrerender& prerender) override;
+  void add(const blink::WebPrerender& prerender) override;
+  void cancel(const blink::WebPrerender& prerender) override;
+  void abandon(const blink::WebPrerender& prerender) override;
 
   // From WebKit, prerender elements launched by renderers in our process.
   std::map<int, blink::WebPrerender> prerenders_;