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

chrome/browser/chromeos/app_mode/kiosk_profile_loader.cc

 // Copyright 2013 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/app_mode/kiosk_profile_loader.h"
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 142 matching lines @@
   login_performer_->set_delegate(NULL);
   ignore_result(login_performer_.release());
 
   // If we are launching a demo session, we need to start MountGuest with the
   // guest username; this is because there are several places in the cros code
   // which rely on the username sent to cryptohome to be $guest. Back in Chrome
   // we switch this back to the demo user name to correctly identify this
   // user as a demo user.
   UserContext context = user_context;
   if (context.GetAccountId() == login::GuestAccountId())
-    context.SetUserID(login::DemoAccountId().GetUserEmail());
+    context.SetAccountId(login::DemoAccountId());
   UserSessionManager::GetInstance()->StartSession(
       context, UserSessionManager::PRIMARY_USER_SESSION,
       false,  // has_auth_cookies
       false,  // Start session for user.
       this);
 }
 
 void KioskProfileLoader::OnAuthFailure(const AuthFailure& error) {
   ReportLaunchResult(LoginFailureToKioskAppLaunchError(error));
 }
@@ skipping 14 matching lines @@
                                            bool browser_launched) {
   // This object could be deleted any time after successfully reporting
   // a profile load, so invalidate the delegate now.
   UserSessionManager::GetInstance()->DelegateDeleted(this);
 
   delegate_->OnProfileLoaded(profile);
   ReportLaunchResult(KioskAppLaunchError::NONE);
 }
 
 }  // namespace chromeos