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

chrome/browser/chromeos/login/users/fake_chrome_user_manager.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 "chrome/browser/chromeos/login/users/fake_chrome_user_manager.h"
 
 #include "base/command_line.h"
 #include "base/sys_info.h"
 #include "chrome/browser/chromeos/login/users/chrome_user_manager.h"
 #include "chrome/browser/chromeos/login/users/chrome_user_manager_util.h"
@@ skipping 10 matching lines @@
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/image/image_skia.h"
 
 namespace chromeos {
 
 class FakeSupervisedUserManager;
 
 FakeChromeUserManager::FakeChromeUserManager()
     : supervised_user_manager_(new FakeSupervisedUserManager),
       bootstrap_manager_(NULL),
-      multi_profile_user_controller_(NULL) {}
+      multi_profile_user_controller_(NULL) {
+  ProfileHelper::SetProfileToUserForTestingEnabled(true);
+}
 
 FakeChromeUserManager::~FakeChromeUserManager() {
+  ProfileHelper::SetProfileToUserForTestingEnabled(false);
 }
 
 const user_manager::User* FakeChromeUserManager::AddUser(
     const AccountId& account_id) {
   return AddUserWithAffiliation(account_id, false);
 }
 
 const user_manager::User* FakeChromeUserManager::AddUserWithAffiliation(
     const AccountId& account_id,
     bool is_affiliated) {
   user_manager::User* user = user_manager::User::CreateRegularUser(account_id);
   user->SetAffiliation(is_affiliated);
   user->set_username_hash(ProfileHelper::GetUserIdHashByUserIdForTesting(
       account_id.GetUserEmail()));
   user->SetStubImage(user_manager::UserImage(
                          *ResourceBundle::GetSharedInstance().GetImageSkiaNamed(
                              IDR_PROFILE_PICTURE_LOADING)),
                      user_manager::User::USER_IMAGE_PROFILE, false);
   users_.push_back(user);
+  chromeos::ProfileHelper::Get()->SetProfileToUserMappingForTesting(user);
   return user;
 }
 
 const user_manager::User* FakeChromeUserManager::AddPublicAccountUser(
     const AccountId& account_id) {
   user_manager::User* user =
       user_manager::User::CreatePublicAccountUser(account_id);
   user->set_username_hash(ProfileHelper::GetUserIdHashByUserIdForTesting(
       account_id.GetUserEmail()));
   user->SetStubImage(user_manager::UserImage(
@@ skipping 200 matching lines @@
   NOTIMPLEMENTED();
   return;
 }
 
 bool FakeChromeUserManager::IsValidDefaultUserImageId(int image_index) const {
   NOTIMPLEMENTED();
   return false;
 }
 
 }  // namespace chromeos