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

chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.cc

 // Copyright 2014 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/wallpaper/wallpaper_manager.h"
 
 #include <stdint.h>
 #include <numeric>
 #include <utility>
 #include <vector>
@@ skipping 22 matching lines @@
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/chromeos/customization/customization_document.h"
 #include "chrome/browser/chromeos/login/startup_utils.h"
 #include "chrome/browser/chromeos/login/wizard_controller.h"
 #include "chrome/browser/chromeos/settings/cros_settings.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
 #include "chromeos/chromeos_switches.h"
 #include "chromeos/cryptohome/async_method_caller.h"
+#include "chromeos/cryptohome/cryptohome_parameters.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/login/user_names.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
 #include "components/prefs/scoped_user_pref_update.h"
 #include "components/signin/core/account_id/account_id.h"
 #include "components/user_manager/user.h"
 #include "components/user_manager/user_image/user_image.h"
 #include "components/user_manager/user_manager.h"
 #include "components/user_manager/user_type.h"
@@ skipping 747 matching lines @@
     const user_manager::UserImage& user_image) {
   const user_manager::User* user =
       user_manager::UserManager::Get()->FindUser(account_id);
   if (!user) {
     NOTREACHED() << "Unknown user.";
     return;
   }
 
   if (user->username_hash().empty()) {
     cryptohome::AsyncMethodCaller::GetInstance()->AsyncGetSanitizedUsername(
-        account_id.GetUserEmail(),
+        cryptohome::Identification(account_id),
         base::Bind(&WallpaperManager::SetCustomWallpaperOnSanitizedUsername,
                    weak_factory_.GetWeakPtr(), account_id, user_image.image(),
                    true /* update wallpaper */));
   } else {
     SetCustomWallpaper(
         account_id, user->username_hash(), "policy-controlled.jpeg",
         wallpaper::WALLPAPER_LAYOUT_CENTER_CROPPED, user_manager::User::POLICY,
         user_image.image(), true /* update wallpaper */);
   }
 }
@@ skipping 277 matching lines @@
           default_large_wallpaper_file.value());
     }
   }
 
   if (need_update_screen) {
     DoSetDefaultWallpaper(EmptyAccountId(), MovableOnDestroyCallbackHolder());
   }
 }
 
 }  // namespace chromeos