cros: Break BaseScreenHandler into two classes.

chrome/browser/chromeos/login/screens/eula_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_EULA_VIEW_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_EULA_VIEW_H_
 
 #include <string>
+#include "chrome/browser/chromeos/login/oobe_screen.h"
 
 namespace chromeos {
 
 class EulaScreen;
 
 // Interface between eula screen and its representation, either WebUI
 // or Views one. Note, do not forget to call OnViewDestroyed in the
 // dtor.
 class EulaView {
  public:
+  constexpr static OobeScreen kScreenId = OobeScreen::SCREEN_OOBE_EULA;
+
   virtual ~EulaView() {}
 
   virtual void Show() = 0;
   virtual void Hide() = 0;
   virtual void Bind(EulaScreen* screen) = 0;
   virtual void Unbind() = 0;
   virtual void OnPasswordFetched(const std::string& tpm_password) = 0;
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_EULA_VIEW_H_