cros: Remove unused method

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

 // Copyright (c) 2014 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_ENABLE_DEBUGGING_SCREEN_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_ENABLE_DEBUGGING_SCREEN_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "chrome/browser/chromeos/login/screens/base_screen.h"
 #include "chrome/browser/chromeos/login/screens/enable_debugging_screen_actor.h"
 
 namespace chromeos {
 
 // Representation independent class that controls screen showing enable
 // debugging screen to users.
 class EnableDebuggingScreen : public BaseScreen,
                               public EnableDebuggingScreenActor::Delegate {
  public:
   EnableDebuggingScreen(BaseScreenDelegate* delegate,
                         EnableDebuggingScreenActor* actor);
   ~EnableDebuggingScreen() override;
 
   // BaseScreen implementation:
-  void PrepareToShow() override;
   void Show() override;
   void Hide() override;
   std::string GetName() const override;
 
   // EnableDebuggingScreenActor::Delegate implementation:
   void OnExit(bool success) override;
   void OnActorDestroyed(EnableDebuggingScreenActor* actor) override;
 
  private:
   EnableDebuggingScreenActor* actor_;
 
   DISALLOW_COPY_AND_ASSIGN(EnableDebuggingScreen);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_ENABLE_DEBUGGING_SCREEN_H_