Add DeviceDisablingManager to manage device disabling

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

 // Copyright 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_DEVICE_DISABLED_SCREEN_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_DEVICE_DISABLED_SCREEN_H_
 
 #include "base/macros.h"
-#include "base/memory/weak_ptr.h"
 #include "chrome/browser/chromeos/login/screens/base_screen.h"
 #include "chrome/browser/chromeos/login/screens/device_disabled_screen_actor.h"
 
 namespace chromeos {
 
 class BaseScreenDelegate;
 
 // Screen informing the user that the device has been disabled by its owner.
 class DeviceDisabledScreen : public BaseScreen,
                              public DeviceDisabledScreenActor::Delegate {
  public:
   DeviceDisabledScreen(BaseScreenDelegate* base_screen_delegate,
                        DeviceDisabledScreenActor* actor);
   ~DeviceDisabledScreen() override;
 
   // BaseScreen:
   void PrepareToShow() override;
   void Show() override;
   void Hide() override;
   std::string GetName() const override;
 
   // DeviceDisabledScreenActor::Delegate:
   void OnActorDestroyed(DeviceDisabledScreenActor* actor) override;
 
  private:
-  // Indicate to the observer that the screen was skipped because the device is
-  // not disabled.
-  void IndicateDeviceNotDisabled();
-
   // Whether the screen is currently showing.
   bool showing_;
 
   DeviceDisabledScreenActor* actor_;
 
-  base::WeakPtrFactory<DeviceDisabledScreen> weak_factory_;
-
   DISALLOW_COPY_AND_ASSIGN(DeviceDisabledScreen);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_DEVICE_DISABLED_SCREEN_H_