Add checks to delegate in SigninScreenHandler

chrome/browser/chromeos/login/webui_login_display_host.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/webui_login_display_host.h"
 
 #include "base/command_line.h"
 #include "chrome/browser/chromeos/login/oobe_display.h"
 #include "chrome/browser/chromeos/login/webui_login_display.h"
 #include "chrome/browser/chromeos/login/webui_login_view.h"
@@ skipping 95 matching lines @@
     LoadURL(GURL(kOobeURL));
 
   BaseLoginDisplayHost::StartWizard(first_screen_name, start_url);
 }
 
 void WebUILoginDisplayHost::StartSignInScreen() {
   if (!login_window_)
     LoadURL(GURL(kLoginURL));
 
   BaseLoginDisplayHost::StartSignInScreen();
+  CHECK(webui_login_display_);
   GetOobeUI()->ShowSigninScreen(webui_login_display_);
 }
 
 void WebUILoginDisplayHost::LoadURL(const GURL& url) {
   if (!login_window_) {
     views::Widget::InitParams params(
         views::Widget::InitParams::TYPE_WINDOW_FRAMELESS);
     params.bounds = background_bounds();
 
     login_window_ = new views::Widget;
@@ skipping 24 matching lines @@
   return static_cast<OobeUI*>(login_view_->GetWebUI());
 }
 
 WizardController* WebUILoginDisplayHost::CreateWizardController() {
   // TODO(altimofeev): ensure that WebUI is ready.
   OobeDisplay* oobe_display = GetOobeUI();
   return new WizardController(this, oobe_display);
 }
 
 }  // namespace chromeos