cros: Remove unused method

chrome/browser/chromeos/login/screens/update_screen.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_UPDATE_SCREEN_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_UPDATE_SCREEN_H_
 
 #include <set>
 
 #include "base/callback.h"
@@ skipping 24 matching lines @@
                      public NetworkPortalDetector::Observer {
  public:
   UpdateScreen(BaseScreenDelegate* base_screen_delegate,
                UpdateView* view,
                pairing_chromeos::HostPairingController* remora_controller);
   ~UpdateScreen() override;
 
   static UpdateScreen* Get(ScreenManager* manager);
 
   // UpdateModel:
-  void PrepareToShow() override;
   void Show() override;
   void Hide() override;
   void Initialize(::login::ScreenContext* context) override;
   void OnViewDestroyed(UpdateView* view) override;
   void OnUserAction(const std::string& action_id) override;
   void OnContextKeyUpdated(const ::login::ScreenContext::KeyType& key) override;
 
   // Starts network check. Made virtual to simplify mocking.
   virtual void StartNetworkCheck();
 
@@ skipping 131 matching lines @@
   ErrorScreen::ConnectRequestCallbackSubscription connect_request_subscription_;
 
   base::WeakPtrFactory<UpdateScreen> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(UpdateScreen);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_UPDATE_SCREEN_H_