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

chrome/browser/ui/webui/chromeos/login/base_screen_handler.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/chromeos/login/base_login_display_host.h"
 #include "chrome/browser/ui/webui/chromeos/login/base_screen_handler.h"
 
 #include "base/values.h"
 
 namespace chromeos {
 
 BaseScreenHandler::BaseScreenHandler() : page_is_ready_(false) {
 }
 
 BaseScreenHandler::~BaseScreenHandler() {
 }
 
 void BaseScreenHandler::InitializeBase() {
   page_is_ready_ = true;
   Initialize();
 }
 
 void BaseScreenHandler::ShowScreen(const char* screen_name,
                                    const base::DictionaryValue* data) {
   if (!web_ui_)
     return;
   DictionaryValue screen_params;
   screen_params.SetString("id", screen_name);
   if (data)
     screen_params.SetWithoutPathExpansion("data", data->DeepCopy());
   web_ui_->CallJavascriptFunction("cr.ui.Oobe.showScreen", screen_params);
 }
 
+
+gfx::NativeWindow BaseScreenHandler::GetNativeWindow() {
+  return BaseLoginDisplayHost::default_host()->GetNativeWindow();
+}
+
 }  // namespace chromeos