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

chrome/browser/chromeos/login/login_browsertest.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 "ash/shell.h"
 #include "ash/system/tray/system_tray.h"
 #include "base/command_line.h"
 #include "base/strings/string_util.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/chromeos/login/login_manager_test.h"
@@ skipping 143 matching lines @@
   }
 
   void PrepareOfflineLogin() {
     bool show_user;
     ASSERT_TRUE(CrosSettings::Get()->GetBoolean(
         kAccountsPrefShowUserNamesOnSignIn, &show_user));
     ASSERT_FALSE(show_user);
 
     StartGaiaAuthOffline();
 
-    UserContext user_context(AccountId::FromUserEmail(kTestUser));
-    user_context.SetGaiaID(kGaiaId);
+    UserContext user_context(
+        AccountId::FromUserEmailGaiaId(kTestUser, kGaiaId));
     user_context.SetKey(Key(kPassword));
     SetExpectedCredentials(user_context);
   }
 };
 
 // Used to make sure that the system tray is visible and within the screen
 // bounds after login.
 void TestSystemTrayIsVisible() {
   ash::SystemTray* tray = ash::Shell::GetInstance()->GetPrimarySystemTray();
   aura::Window* primary_win = ash::Shell::GetPrimaryRootWindow();
@@ skipping 78 matching lines @@
   content::WindowedNotificationObserver session_start_waiter(
       chrome::NOTIFICATION_SESSION_STARTED,
       content::NotificationService::AllSources());
   SubmitGaiaAuthOfflineForm(kTestUser, kPassword);
   session_start_waiter.Wait();
 
   TestSystemTrayIsVisible();
 }
 
 }  // namespace chromeos