Use DCHECKs when observing only a single notification.

chrome/browser/chromeos/login/signin_screen_controller.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/login/signin_screen_controller.h"
 
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/chromeos/login/lock/screen_locker.h"
 #include "chrome/browser/chromeos/login/screens/chrome_user_selection_screen.h"
 #include "chrome/browser/chromeos/login/ui/views/user_board_view.h"
@@ skipping 76 matching lines @@
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
   if (type == chrome::NOTIFICATION_SESSION_STARTED) {
     // Stop listening to any notification once session has started.
     // Sign in screen objects are marked for deletion with DeleteSoon so
     // make sure no object would be used after session has started.
     // http://crbug.com/125276
     registrar_.RemoveAll();
     return;
-  } else if (type == chrome::NOTIFICATION_LOGIN_USER_IMAGE_CHANGED) {
+  }
+  if (type == chrome::NOTIFICATION_LOGIN_USER_IMAGE_CHANGED) {
     user_selection_screen_->OnUserImageChanged(
         *content::Details<user_manager::User>(details).ptr());
     return;
   }
 }
 
 }  // namespace chromeos