Standardize usage of virtual/override/final in content/browser/

content/browser/browser_thread_impl.h

Index: content/browser/browser_thread_impl.h
diff --git a/content/browser/browser_thread_impl.h b/content/browser/browser_thread_impl.h
index fca4379ffc68aa2fb8f5537bfbe2f6c562cb359f..72915ea393f21ab1020f4255e3da155651283448 100644
--- a/content/browser/browser_thread_impl.h
+++ b/content/browser/browser_thread_impl.h
@@ -23,14 +23,14 @@ class CONTENT_EXPORT BrowserThreadImpl : public BrowserThread,
   // thread already exists.
   BrowserThreadImpl(BrowserThread::ID identifier,
                     base::MessageLoop* message_loop);
-  virtual ~BrowserThreadImpl();
+  ~BrowserThreadImpl() override;
 
   static void ShutdownThreadPool();
 
  protected:
-  virtual void Init() override;
-  virtual void Run(base::MessageLoop* message_loop) override;
-  virtual void CleanUp() override;
+  void Init() override;
+  void Run(base::MessageLoop* message_loop) override;
+  void CleanUp() override;
 
  private:
   // We implement all the functionality of the public BrowserThread