cros: Break BaseScreenHandler into two classes.

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

 // Copyright (c) 2013 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_WRONG_HWID_SCREEN_VIEW_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_WRONG_HWID_SCREEN_VIEW_H_
 
 #include <string>
+#include "chrome/browser/chromeos/login/oobe_screen.h"
 
 namespace chromeos {
 
 // Interface between wrong HWID screen and its representation.
 // Note, do not forget to call OnViewDestroyed in the dtor.
 class WrongHWIDScreenView {
  public:
   // Allows us to get info from wrong HWID screen that we need.
   class Delegate {
    public:
     virtual ~Delegate() {}
 
     // Called when screen is exited.
     virtual void OnExit() = 0;
 
     // This method is called, when view is being destroyed. Note, if Delegate
     // is destroyed earlier then it has to call SetDelegate(NULL).
     virtual void OnViewDestroyed(WrongHWIDScreenView* view) = 0;
   };
 
+  constexpr static OobeScreen kScreenId = OobeScreen::SCREEN_WRONG_HWID;
+
   virtual ~WrongHWIDScreenView() {}
 
   virtual void Show() = 0;
   virtual void Hide() = 0;
   virtual void SetDelegate(Delegate* delegate) = 0;
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_WRONG_HWID_SCREEN_VIEW_H_