[cros,de-hack] Get rid of singleton for the WebUILoginScreen.

chrome/browser/chromeos/login/login_display_host.h

 // Copyright (c) 2011 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_LOGIN_DISPLAY_HOST_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_LOGIN_DISPLAY_HOST_H_
 #pragma once
 
 #include <string>
 
 #include "chrome/browser/chromeos/login/background_view.h"
 #include "chrome/browser/chromeos/customization_document.h"
 #include "chrome/browser/chromeos/login/login_display.h"
 #include "googleurl/src/gurl.h"
 #include "ui/gfx/native_widget_types.h"
 
 namespace chromeos {
 
 // An interface that defines OOBE/login screen host.
 // Host encapsulates implementation specific background window (views/WebUI),
 // OOBE/login controllers, views/WebUI UI implementation (such as LoginDisplay).
 class LoginDisplayHost {
  public:
   virtual ~LoginDisplayHost() {}
 
   // Creates UI implementation specific login display instance (views/WebUI).
+  // The caller takes ownership of the returned value.
   virtual LoginDisplay* CreateLoginDisplay(
-      LoginDisplay::Delegate* delegate) const = 0;
+      LoginDisplay::Delegate* delegate) = 0;
 
   // Returns corresponding native window.
   // TODO(nkostylev): Might be refactored, move to views-specific code.
   virtual gfx::NativeWindow GetNativeWindow() const = 0;
 
   // Called when browsing session starts so
   // LoginDisplayHost instance may delete itself.
   virtual void OnSessionStart() = 0;
 
   // TODO(nkostylev): Refactor enum.
@@ skipping 22 matching lines @@
       const std::string& first_screen_name,
       const GURL& start_url) = 0;
 
   // Starts sign in screen.
   virtual void StartSignInScreen() = 0;
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_LOGIN_DISPLAY_HOST_H_