Standardize usage of virtual/override/final in content/

content/shell/browser/notify_done_forwarder.h

Index: content/shell/browser/notify_done_forwarder.h
diff --git a/content/shell/browser/notify_done_forwarder.h b/content/shell/browser/notify_done_forwarder.h
index 75beb8d0b0f27f47fcb60c0e8d7faf8fe350e51b..58a88697cf5186ce5c6fabbbe075b3b3e9b14350 100644
--- a/content/shell/browser/notify_done_forwarder.h
+++ b/content/shell/browser/notify_done_forwarder.h
@@ -14,10 +14,10 @@ namespace content {
 class NotifyDoneForwarder : public WebContentsObserver,
                             public WebContentsUserData<NotifyDoneForwarder> {
  public:
-  virtual ~NotifyDoneForwarder();
+  ~NotifyDoneForwarder() override;
 
   // WebContentsObserver implementation.
-  virtual bool OnMessageReceived(const IPC::Message& message) override;
+  bool OnMessageReceived(const IPC::Message& message) override;
 
  private:
   friend class WebContentsUserData<NotifyDoneForwarder>;