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

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

Index: chrome/browser/ui/webui/chromeos/login/base_screen_handler.cc
diff --git a/chrome/browser/ui/webui/chromeos/login/base_screen_handler.cc b/chrome/browser/ui/webui/chromeos/login/base_screen_handler.cc
index 474a1d8daac13092bcd9cf12e2c5e56fefec4059..3d0bca9a9e11a31eea32de42603fed19799b344a 100644
--- a/chrome/browser/ui/webui/chromeos/login/base_screen_handler.cc
+++ b/chrome/browser/ui/webui/chromeos/login/base_screen_handler.cc
@@ -2,6 +2,7 @@
 // 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"
@@ -30,4 +31,9 @@ void BaseScreenHandler::ShowScreen(const char* screen_name,
   web_ui_->CallJavascriptFunction("cr.ui.Oobe.showScreen", screen_params);
 }
 
+
+gfx::NativeWindow BaseScreenHandler::GetNativeWindow() {
+  return BaseLoginDisplayHost::default_host()->GetNativeWindow();
+}
+
 }  // namespace chromeos