Revert of ChromeOS login webui refactoring: split user selection/gaia login screens.

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

-// Copyright (c) 2012 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_GAIA_SCREEN_H_
-#define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_GAIA_SCREEN_H_
-
-#include <string>
-
-#include "base/bind.h"
-#include "base/compiler_specific.h"
-
-namespace chromeos {
-
-class LoginDisplayWebUIHandler;
-
-// This class represents GAIA screen: login screen that is responsible for
-// GAIA-based sign-in.
-class GaiaScreen {
- public:
-  GaiaScreen();
-  virtual ~GaiaScreen();
-  void SetHandler(LoginDisplayWebUIHandler* handler);
-
- private:
-  LoginDisplayWebUIHandler* handler_;
-
-  DISALLOW_COPY_AND_ASSIGN(GaiaScreen);
-};
-
-}  // namespace chromeos
-
-#endif  // CHROME_BROWSER_CHROMEOS_LOGIN_SCREENS_GAIA_SCREEN_H_