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

chrome/browser/ui/webui/chromeos/login/oobe_ui.cc

 // 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.
 
 #include "chrome/browser/ui/webui/chromeos/login/oobe_ui.h"
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 218 matching lines @@
   // Note, handlers_[0] is a GenericHandler used by the WebUI.
   for (size_t i = 1; i < handlers_.size(); ++i) {
     static_cast<BaseScreenHandler*>(handlers_[i])->InitializeBase();
   }
 }
 
 void OobeUI::ShowOobeUI(bool show) {
   core_handler_->ShowOobeUI(show);
 }
 
-void OobeUI::ShowSigninScreen() {
+void OobeUI::ShowSigninScreen(SigninScreenHandlerDelegate* delegate) {
+  signin_screen_handler_->SetDelegate(delegate);
   signin_screen_handler_->Show(core_handler_->show_oobe_ui());
 }
 
 void OobeUI::OnLoginPromptVisible() {
   user_image_screen_actor_->CheckCameraPresence();
 }
 
 }  // namespace chromeos