Standardize usage of virtual/override/final in content/

content/public/test/test_browser_thread.cc

Index: content/public/test/test_browser_thread.cc
diff --git a/content/public/test/test_browser_thread.cc b/content/public/test/test_browser_thread.cc
index ac3311c497128ef36512a654b6630be649006b41..ac67480fe5cd36b6cd515d866656e2687983a9f1 100644
--- a/content/public/test/test_browser_thread.cc
+++ b/content/public/test/test_browser_thread.cc
@@ -23,16 +23,14 @@ class TestBrowserThreadImpl : public BrowserThreadImpl {
       : BrowserThreadImpl(identifier, message_loop),
         notification_service_(NULL) {}
 
-  virtual ~TestBrowserThreadImpl() {
-    Stop();
-  }
+  ~TestBrowserThreadImpl() override { Stop(); }
 
-  virtual void Init() override {
+  void Init() override {
     notification_service_ = new NotificationServiceImpl;
     BrowserThreadImpl::Init();
   }
 
-  virtual void CleanUp() override {
+  void CleanUp() override {
     delete notification_service_;
     notification_service_ = NULL;
     BrowserThreadImpl::CleanUp();