We should use UserID object to identify users instead of username.

chrome/browser/extensions/external_provider_impl.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 "chrome/browser/extensions/external_provider_impl.h"
 
 #include <set>
 #include <vector>
 
 #include "base/command_line.h"
@@ skipping 418 matching lines @@
   extensions::Manifest::Location crx_location = Manifest::INVALID_LOCATION;
 #if defined(OS_CHROMEOS)
   policy::BrowserPolicyConnectorChromeOS* connector =
       g_browser_process->platform_part()->browser_policy_connector_chromeos();
   bool is_chrome_os_public_session = false;
   const user_manager::User* user =
       chromeos::ProfileHelper::Get()->GetUserByProfile(profile);
   policy::DeviceLocalAccount::Type account_type;
   if (user &&
       connector->IsEnterpriseManaged() &&
-      policy::IsDeviceLocalAccountUser(user->email(), &account_type)) {
+      policy::IsDeviceLocalAccountUser(user->GetUserID(), &account_type)) {
     if (account_type == policy::DeviceLocalAccount::TYPE_PUBLIC_SESSION)
       is_chrome_os_public_session = true;
     policy::DeviceLocalAccountPolicyBroker* broker =
         connector->GetDeviceLocalAccountPolicyService()->GetBrokerForUser(
-            user->email());
+            user->GetUserID());
     if (broker) {
       external_loader = broker->extension_loader();
       crx_location = Manifest::EXTERNAL_POLICY;
     } else {
       NOTREACHED();
     }
   } else {
     external_loader = new ExternalPolicyLoader(
         ExtensionManagementFactory::GetForBrowserContext(profile),
         ExternalPolicyLoader::FORCED);
@@ skipping 186 matching lines @@
       new ExternalProviderImpl(
           service,
           new ExternalComponentLoader(profile),
           profile,
           Manifest::INVALID_LOCATION,
           Manifest::EXTERNAL_COMPONENT,
           Extension::FROM_WEBSTORE | Extension::WAS_INSTALLED_BY_DEFAULT)));
 }
 
 }  // namespace extensions