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

chrome/browser/chromeos/policy/policy_cert_service_factory.cc

 // Copyright 2013 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/policy/policy_cert_service_factory.h"
 
 #include "base/memory/singleton.h"
 #include "base/prefs/pref_registry_simple.h"
 #include "base/prefs/pref_service.h"
 #include "base/prefs/scoped_user_pref_update.h"
@@ skipping 29 matching lines @@
   return service->CreatePolicyCertVerifier();
 }
 
 // static
 PolicyCertServiceFactory* PolicyCertServiceFactory::GetInstance() {
   return Singleton<PolicyCertServiceFactory>::get();
 }
 
 // static
 void PolicyCertServiceFactory::SetUsedPolicyCertificates(
-    const std::string& user_id) {
+    const user_manager::UserID& user_id) {
   if (UsedPolicyCertificates(user_id))
     return;
   ListPrefUpdate update(g_browser_process->local_state(),
                         prefs::kUsedPolicyCertificates);
-  update->AppendString(user_id);
+  update->AppendString(user_id.GetUserEmail());
 }
 
 // static
 void PolicyCertServiceFactory::ClearUsedPolicyCertificates(
-    const std::string& user_id) {
+    const user_manager::UserID& user_id) {
   ListPrefUpdate update(g_browser_process->local_state(),
                         prefs::kUsedPolicyCertificates);
-  update->Remove(base::StringValue(user_id), NULL);
+  update->Remove(base::StringValue(user_id.GetUserEmail()), NULL);
 }
 
 // static
 bool PolicyCertServiceFactory::UsedPolicyCertificates(
-    const std::string& user_id) {
-  base::StringValue value(user_id);
+    const user_manager::UserID& user_id) {
+  base::StringValue value(user_id.GetUserEmail());
   const base::ListValue* list =
       g_browser_process->local_state()->GetList(prefs::kUsedPolicyCertificates);
   if (!list) {
     NOTREACHED();
     return false;
   }
   return list->Find(value) != list->end();
 }
 
 // static
@@ skipping 21 matching lines @@
   if (!user)
     return NULL;
 
   // Backwards compatibility: profiles that used policy-pushed certificates used
   // to have this condition marked in their prefs. This signal has moved to
   // local_state though, to support checking it before the profile is loaded.
   // Check the profile here and update the local_state, if appropriate.
   // TODO(joaodasilva): remove this, eventually.
   PrefService* prefs = profile->GetOriginalProfile()->GetPrefs();
   if (prefs->GetBoolean(prefs::kUsedPolicyCertificatesOnce)) {
-    SetUsedPolicyCertificates(user->email());
+    SetUsedPolicyCertificates(user->GetUserID());
     prefs->ClearPref(prefs::kUsedPolicyCertificatesOnce);
 
     if (user_manager->GetLoggedInUsers().size() > 1u) {
       // This login should not have been allowed. After rebooting, local_state
       // will contain the updated list of users that used policy-pushed
       // certificates and this won't happen again.
       // Note that a user becomes logged in before his profile is created.
       LOG(ERROR) << "Shutdown session because a tainted profile was added.";
       g_browser_process->local_state()->CommitPendingWrite();
       prefs->CommitPendingWrite();
       chrome::AttemptUserExit();
     }
   }
 
   UserNetworkConfigurationUpdater* net_conf_updater =
       UserNetworkConfigurationUpdaterFactory::GetForProfile(profile);
   if (!net_conf_updater)
     return NULL;
 
-  return new PolicyCertService(user->email(), net_conf_updater, user_manager);
+  return new PolicyCertService(user->GetUserID(), net_conf_updater, user_manager);
 }
 
 content::BrowserContext* PolicyCertServiceFactory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   return chrome::GetBrowserContextOwnInstanceInIncognito(context);
 }
 
 void PolicyCertServiceFactory::RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
   // TODO(joaodasilva): this is used for backwards compatibility.
   // Remove once it's not necessary anymore.
   registry->RegisterBooleanPref(prefs::kUsedPolicyCertificatesOnce, false);
 }
 
 bool PolicyCertServiceFactory::ServiceIsNULLWhileTesting() const {
   return true;
 }
 
 }  // namespace policy