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

chrome/browser/chromeos/login/users/fake_chrome_user_manager.cc

Index: chrome/browser/chromeos/login/users/fake_chrome_user_manager.cc
diff --git a/chrome/browser/chromeos/login/users/fake_chrome_user_manager.cc b/chrome/browser/chromeos/login/users/fake_chrome_user_manager.cc
index 8d4f8d77cec931c1808a60caed10d2d745e2725e..7e79232fc87961c690c6afb18697fe9e65e6dbbd 100644
--- a/chrome/browser/chromeos/login/users/fake_chrome_user_manager.cc
+++ b/chrome/browser/chromeos/login/users/fake_chrome_user_manager.cc
@@ -28,9 +28,12 @@ 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(
@@ -50,6 +53,7 @@ const user_manager::User* FakeChromeUserManager::AddUserWithAffiliation(
                              IDR_PROFILE_PICTURE_LOADING)),
                      user_manager::User::USER_IMAGE_PROFILE, false);
   users_.push_back(user);
+  chromeos::ProfileHelper::Get()->SetProfileToUserMappingForTesting(user);
   return user;
 }