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

remoting/host/disconnect_window_win.cc

Index: remoting/host/disconnect_window_win.cc
diff --git a/remoting/host/disconnect_window_win.cc b/remoting/host/disconnect_window_win.cc
index fd789d4f54662f6ee2b6f4b834e4f2e6fb35c7a7..7617b091ad0413e7f2d142da04b4f8150e29cec5 100644
--- a/remoting/host/disconnect_window_win.cc
+++ b/remoting/host/disconnect_window_win.cc
@@ -35,10 +35,10 @@ const int kWindowTextMargin = 8;
 class DisconnectWindowWin : public HostWindow {
  public:
   DisconnectWindowWin();
-  virtual ~DisconnectWindowWin();
+  ~DisconnectWindowWin() override;
 
   // HostWindow overrides.
-  virtual void Start(
+  void Start(
       const base::WeakPtr<ClientSessionControl>& client_session_control)
       override;