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

chrome/browser/extensions/extension_system_impl.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/extensions/extension_system_impl.h"
 
 #include "base/base_switches.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
@@ skipping 101 matching lines @@
 
   rules_store_.reset(new StateStore(
       profile_,
       profile_->GetPath().AppendASCII(extensions::kRulesStoreName),
       false));
 
 #if defined(OS_CHROMEOS)
   const user_manager::User* user =
       user_manager::UserManager::Get()->GetActiveUser();
   policy::DeviceLocalAccount::Type device_local_account_type;
-  if (user && policy::IsDeviceLocalAccountUser(user->email(),
+  if (user && policy::IsDeviceLocalAccountUser(user->GetUserID(),
                                                &device_local_account_type)) {
     device_local_account_management_policy_provider_.reset(
         new chromeos::DeviceLocalAccountManagementPolicyProvider(
             device_local_account_type));
   }
 #endif  // defined(OS_CHROMEOS)
 }
 
 void ExtensionSystemImpl::Shared::RegisterManagementPolicyProviders() {
   management_policy_->RegisterProviders(
@@ skipping 418 matching lines @@
 void ExtensionSystemImpl::UnregisterExtensionWithRequestContexts(
     const std::string& extension_id,
     const UnloadedExtensionInfo::Reason reason) {
   BrowserThread::PostTask(
       BrowserThread::IO,
       FROM_HERE,
       base::Bind(&InfoMap::RemoveExtension, info_map(), extension_id, reason));
 }
 
 }  // namespace extensions