cros: Break BaseScreenHandler into two classes.

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

 // Copyright 2017 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_ARC_KIOSK_SPLASH_SCREEN_VIEW_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_ARC_KIOSK_SPLASH_SCREEN_VIEW_H_
 
+#include "chrome/browser/chromeos/login/oobe_screen.h"
+
 namespace chromeos {
 
 // Interface for UI implemenations of the ArcKioskSplashScreen.
 class ArcKioskSplashScreenView {
  public:
   enum class ArcKioskState {
     STARTING_SESSION,
     WAITING_APP_LAUNCH,
     WAITING_APP_WINDOW,
   };
 
   class Delegate {
    public:
     Delegate() = default;
     // Invoked when the launch bailout shortcut key is pressed.
     virtual void OnCancelArcKioskLaunch() = 0;
 
    protected:
     virtual ~Delegate() = default;
 
    private:
     DISALLOW_COPY_AND_ASSIGN(Delegate);
   };
 
+  constexpr static OobeScreen kScreenId = OobeScreen::SCREEN_ARC_KIOSK_SPLASH;
+
   ArcKioskSplashScreenView() = default;
 
   virtual ~ArcKioskSplashScreenView() = default;
 
   // Shows the contents of the screen.
   virtual void Show() = 0;
 
   // Set the current ARC kiosk state.
   virtual void UpdateArcKioskState(ArcKioskState state) = 0;
 
   // Sets screen this view belongs to.
   virtual void SetDelegate(Delegate* delegate) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ArcKioskSplashScreenView);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_ARC_KIOSK_SPLASH_SCREEN_VIEW_H_