We should use UserID object to identify users instead of username.

chrome/browser/signin/signin_error_notifier_ash.cc

 // Copyright 2014 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/signin/signin_error_notifier_ash.h"
 
 #include "ash/shell.h"
 #include "ash/shell_delegate.h"
 #include "ash/system/system_notifier.h"
 #include "base/logging.h"
 #include "base/strings/string16.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/lifetime/application_lifetime.h"
 #include "chrome/browser/notifications/notification.h"
 #include "chrome/browser/notifications/notification_delegate.h"
 #include "chrome/browser/notifications/notification_ui_manager.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/ash/multi_user/multi_user_util.h"
 #include "chrome/browser/ui/browser_tabstrip.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/chrome_pages.h"
 #include "chrome/browser/ui/scoped_tabbed_browser_displayer.h"
 #include "chrome/browser/ui/webui/signin/login_ui_service.h"
 #include "chrome/browser/ui/webui/signin/login_ui_service_factory.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/grit/chromium_strings.h"
 #include "chrome/grit/generated_resources.h"
+#include "components/user_manager/user_id.h"
 #include "grit/theme_resources.h"
 #include "third_party/WebKit/public/web/WebTextDirection.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/message_center/notification.h"
 #include "ui/message_center/notification_delegate.h"
 
 #if defined(OS_CHROMEOS)
 #include "chrome/browser/chromeos/login/user_flow.h"
 #include "chrome/browser/chromeos/login/users/chrome_user_manager.h"
@@ skipping 129 matching lines @@
 
   // Set the delegate for the notification's sign-out button.
   SigninNotificationDelegate* delegate =
       new SigninNotificationDelegate(notification_id_, profile_);
 
   message_center::NotifierId notifier_id(
       message_center::NotifierId::SYSTEM_COMPONENT,
       kProfileSigninNotificationId);
 
   // Set |profile_id| for multi-user notification blocker.
-  notifier_id.profile_id = multi_user_util::GetUserIDFromProfile(profile_);
+  notifier_id.profile_id = multi_user_util::GetUserIDFromProfile(profile_).GetUserEmail();
 
   Notification notification(
       message_center::NOTIFICATION_TYPE_SIMPLE,
       GURL(notification_id_),
       l10n_util::GetStringUTF16(IDS_SIGNIN_ERROR_BUBBLE_VIEW_TITLE),
       GetMessageBody(),
       ui::ResourceBundle::GetSharedInstance().GetImageNamed(
           IDR_NOTIFICATION_ALERT),
       notifier_id,
       base::string16(),  // display_source
@@ skipping 27 matching lines @@
       return l10n_util::GetStringUTF16(
           IDS_SYNC_UNAVAILABLE_ERROR_BUBBLE_VIEW_MESSAGE);
       break;
 
     // Generic message for "other" errors.
     default:
       return l10n_util::GetStringUTF16(
           IDS_SYNC_OTHER_SIGN_IN_ERROR_BUBBLE_VIEW_MESSAGE);
   }
 }