Check for login screen availibility before showing spinner.

chrome/browser/chromeos/kiosk_mode/kiosk_mode_screensaver.cc

 // Copyright (c) 2012 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/kiosk_mode/kiosk_mode_screensaver.h"
 
 #include "ash/screensaver/screensaver_view.h"
 #include "ash/shell.h"
 #include "ash/wm/user_activity_detector.h"
 #include "base/bind.h"
@@ skipping 181 matching lines @@
     ShutdownKioskModeScreensaver();
   }
 }
 
 void KioskModeScreensaver::OnUserActivity() {
   // We don't want to handle further user notifications; we'll either login
   // the user and close out or or at least close the screensaver.
   ash::Shell::GetInstance()->user_activity_detector()->RemoveObserver(this);
 
   // Find the retail mode login page.
-  CHECK(WebUILoginDisplayHost::default_host());
-  WebUILoginDisplayHost* webui_host =
-      static_cast<WebUILoginDisplayHost*>(
-          WebUILoginDisplayHost::default_host());
-  OobeUI* oobe_ui = webui_host->GetOobeUI();
+  if (WebUILoginDisplayHost::default_host()) {
+    WebUILoginDisplayHost* webui_host =
+        static_cast<WebUILoginDisplayHost*>(
+            WebUILoginDisplayHost::default_host());
+    OobeUI* oobe_ui = webui_host->GetOobeUI();
 
-  // Show the login spinner.
-  CHECK(oobe_ui);
-  oobe_ui->ShowRetailModeLoginSpinner();
+    // Show the login spinner.
+    if (oobe_ui)
+      oobe_ui->ShowRetailModeLoginSpinner();
 
-  // Close the screensaver, our login spinner is already showing.
-  ash::CloseScreensaver();
+    // Close the screensaver, our login spinner is already showing.
+    ash::CloseScreensaver();
 
-  // Log us in.
-  ExistingUserController* controller =
-      ExistingUserController::current_controller();
-  CHECK(controller);
-  controller->LoginAsDemoUser();
+    // Log us in.
+    ExistingUserController* controller =
+        ExistingUserController::current_controller();
+    if (controller && !chromeos::UserManager::Get()->IsUserLoggedIn())
+      controller->LoginAsDemoUser();
+  } else {
+    // No default host for the WebUiLoginDisplay means that we're already in the
+    // process of logging in - shut down screensaver and do nothing else.
+    ash::CloseScreensaver();
+  }
 
   ShutdownKioskModeScreensaver();
 }
 
 static KioskModeScreensaver* g_kiosk_mode_screensaver = NULL;
 
 void InitializeKioskModeScreensaver() {
   if (g_kiosk_mode_screensaver) {
     LOG(WARNING) << "Screensaver was already initialized";
     return;
   }
 
   g_kiosk_mode_screensaver = new KioskModeScreensaver();
 }
 
 void ShutdownKioskModeScreensaver() {
   delete g_kiosk_mode_screensaver;
   g_kiosk_mode_screensaver = NULL;
 }
 
 }  // namespace chromeos