cros: Break BaseScreenHandler into two classes.

chrome/browser/chromeos/login/screens/device_disabled_screen_view.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_VIEW_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_DEVICE_DISABLED_SCREEN_VIEW_H_
 
 #include <string>
+#include "chrome/browser/chromeos/login/oobe_screen.h"
 
 namespace chromeos {
 
 // Interface between the device disabled screen and its representation.
 class DeviceDisabledScreenView {
  public:
   // Allows the representation to access information about the screen.
   class Delegate {
    public:
     virtual ~Delegate() {}
 
     // Called when the view is being destroyed. Note that if the Delegate is
     // destroyed first, it must call SetDelegate(nullptr).
     virtual void OnViewDestroyed(DeviceDisabledScreenView* view) = 0;
 
     // Returns the domain that owns the device.
     virtual const std::string& GetEnrollmentDomain() const = 0;
 
     // Returns the message that should be shown to the user.
     virtual const std::string& GetMessage() const = 0;
   };
 
+  constexpr static OobeScreen kScreenId = OobeScreen::SCREEN_DEVICE_DISABLED;
+
   virtual ~DeviceDisabledScreenView() {}
 
   virtual void Show() = 0;
   virtual void Hide() = 0;
   virtual void SetDelegate(Delegate* delegate) = 0;
   virtual void UpdateMessage(const std::string& message) = 0;
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_DEVICE_DISABLED_SCREEN_VIEW_H_