ChromeOS cryptohome should be able to use gaia id as user identifier.

chrome/browser/download/notification/download_notification_browsertest.cc

 // Copyright 2015 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 <stddef.h>
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 1176 matching lines @@
   Profile* GetProfileByIndex(int index) {
     return chromeos::ProfileHelper::GetProfileByUserIdHash(
         kTestAccounts[index].hash);
   }
 
   // Adds a new user for testing to the current session.
   void AddUser(const TestAccountInfo& info, bool log_in) {
     user_manager::UserManager* const user_manager =
         user_manager::UserManager::Get();
     if (log_in)
-      user_manager->UserLoggedIn(AccountId::FromUserEmail(info.email),
-                                 info.hash, false);
-    user_manager->SaveUserDisplayName(AccountId::FromUserEmail(info.email),
-                                      base::UTF8ToUTF16(info.display_name));
+      user_manager->UserLoggedIn(
+          AccountId::FromUserEmailGaiaId(info.email, info.gaia_id), info.hash,
+          false);
+    user_manager->SaveUserDisplayName(
+        AccountId::FromUserEmailGaiaId(info.email, info.gaia_id),
+        base::UTF8ToUTF16(info.display_name));
     SigninManagerFactory::GetForProfile(
         chromeos::ProfileHelper::GetProfileByUserIdHash(info.hash))
             ->SetAuthenticatedAccountInfo(info.gaia_id, info.email);
   }
 };
 
 IN_PROC_BROWSER_TEST_F(MultiProfileDownloadNotificationTest,
                        PRE_DownloadMultipleFiles) {
   AddAllUsers();
 }
@@ skipping 95 matching lines @@
   EXPECT_EQ(message_center::NOTIFICATION_TYPE_BASE_FORMAT,
             GetNotification(notification_id_user1)->type());
   EXPECT_EQ(message_center::NOTIFICATION_TYPE_BASE_FORMAT,
             GetNotification(notification_id_user2_1)->type());
   // Normal notifications for user2.
   EXPECT_EQ(message_center::NOTIFICATION_TYPE_BASE_FORMAT,
             GetNotification(notification_id_user2_1)->type());
   EXPECT_EQ(message_center::NOTIFICATION_TYPE_BASE_FORMAT,
             GetNotification(notification_id_user2_2)->type());
 }