Standardize usage of virtual/override/final in remoting/

remoting/host/curtain_mode_mac.cc

Index: remoting/host/curtain_mode_mac.cc
diff --git a/remoting/host/curtain_mode_mac.cc b/remoting/host/curtain_mode_mac.cc
index 57a5b331c56a746db55b08c450857fe874b2bd2f..b0718e88364bf29ebcc86699ea8c3aa30413ed06 100644
--- a/remoting/host/curtain_mode_mac.cc
+++ b/remoting/host/curtain_mode_mac.cc
@@ -226,10 +226,10 @@ class CurtainModeMac : public CurtainMode {
       scoped_refptr<base::SingleThreadTaskRunner> caller_task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner,
       base::WeakPtr<ClientSessionControl> client_session_control);
-  virtual ~CurtainModeMac();
+  ~CurtainModeMac() override;
 
   // Overriden from CurtainMode.
-  virtual bool Activate() override;
+  bool Activate() override;
 
  private:
   scoped_refptr<SessionWatcher> session_watcher_;