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

chrome/browser/chromeos/login/screens/user_selection_screen.cc

Index: chrome/browser/chromeos/login/screens/user_selection_screen.cc
diff --git a/chrome/browser/chromeos/login/screens/user_selection_screen.cc b/chrome/browser/chromeos/login/screens/user_selection_screen.cc
index 814faee0196f4f8509c36bf03975a9ca2b9b8d0e..18befd404db9a204778905847edb46f997bc14b5 100644
--- a/chrome/browser/chromeos/login/screens/user_selection_screen.cc
+++ b/chrome/browser/chromeos/login/screens/user_selection_screen.cc
@@ -143,14 +143,14 @@ void UserSelectionScreen::FillUserDictionary(
     AuthType auth_type,
     const std::vector<std::string>* public_session_recommended_locales,
     base::DictionaryValue* user_dict) {
-  const user_manager::UserID user_id = user->email();
+  const user_manager::UserID user_id = user->GetUserID();
   const bool is_public_session =
       user->GetType() == user_manager::USER_TYPE_PUBLIC_ACCOUNT;
   const bool is_legacy_supervised_user =
       user->GetType() == user_manager::USER_TYPE_SUPERVISED;
   const bool is_child_user = user->GetType() == user_manager::USER_TYPE_CHILD;
 
-  user_dict->SetString(kKeyUsername, user_id);
+  user_dict->SetString(kKeyUsername, user_id.GetUserEmail());
   user_dict->SetString(kKeyEmailAddress, user->display_email());
   user_dict->SetString(kKeyDisplayName, user->GetDisplayName());
   user_dict->SetBoolean(kKeyPublicAccount, is_public_session);
@@ -174,7 +174,7 @@ void UserSelectionScreen::FillUserDictionary(
 void UserSelectionScreen::FillKnownUserPrefs(user_manager::User* user,
                                              base::DictionaryValue* user_dict) {
   std::string gaia_id;
-  if (user_manager::UserManager::Get()->FindGaiaID(user->email(), &gaia_id)) {
+  if (user_manager::UserManager::Get()->FindGaiaID(user->GetUserID(), &gaia_id)) {
     user_dict->SetString(kKeyGaiaID, gaia_id);
   }
 }
@@ -184,7 +184,7 @@ void UserSelectionScreen::FillMultiProfileUserPrefs(
     user_manager::User* user,
     base::DictionaryValue* user_dict,
     bool is_signin_to_add) {
-  const std::string& user_id = user->email();
+  const user_manager::UserID& user_id = user->GetUserID();
 
   if (is_signin_to_add) {
     MultiProfileUserController* multi_profile_user_controller =
@@ -240,7 +240,7 @@ bool UserSelectionScreen::ShouldForceOnlineSignIn(
   // At this point the reason for invalid token should be already set. If not,
   // this might be a leftover from an old version.
   if (token_status == user_manager::User::OAUTH2_TOKEN_STATUS_INVALID)
-    RecordReauthReason(user->email(), ReauthReason::OTHER);
+    RecordReauthReason(user->GetUserID(), ReauthReason::OTHER);
 
   return user->force_online_signin() ||
          (token_status == user_manager::User::OAUTH2_TOKEN_STATUS_INVALID) ||
@@ -265,21 +265,21 @@ void UserSelectionScreen::Init(const user_manager::UserList& users,
     activity_detector->AddObserver(this);
 }
 
-void UserSelectionScreen::OnBeforeUserRemoved(const std::string& username) {
+void UserSelectionScreen::OnBeforeUserRemoved(const user_manager::UserID& user_id) {
   for (user_manager::UserList::iterator it = users_.begin(); it != users_.end();
        ++it) {
-    if ((*it)->email() == username) {
+    if ((*it)->GetUserID() == user_id) {
       users_.erase(it);
       break;
     }
   }
 }
 
-void UserSelectionScreen::OnUserRemoved(const std::string& username) {
+void UserSelectionScreen::OnUserRemoved(const user_manager::UserID& user_id) {
   if (!handler_)
     return;
 
-  handler_->OnUserRemoved(username);
+  handler_->OnUserRemoved(user_id);
 }
 
 void UserSelectionScreen::OnUserImageChanged(const user_manager::User& user) {
@@ -312,17 +312,17 @@ void UserSelectionScreen::OnUserActivity(const ui::Event* event) {
 // static
 const user_manager::UserList UserSelectionScreen::PrepareUserListForSending(
     const user_manager::UserList& users,
-    std::string owner,
+    const user_manager::UserID& owner,
     bool is_signin_to_add) {
   user_manager::UserList users_to_send;
-  bool has_owner = owner.size() > 0;
+  bool has_owner = !owner.empty();
   size_t max_non_owner_users = has_owner ? kMaxUsers - 1 : kMaxUsers;
   size_t non_owner_count = 0;
 
   for (user_manager::UserList::const_iterator it = users.begin();
        it != users.end();
        ++it) {
-    const std::string& user_id = (*it)->email();
+    const user_manager::UserID& user_id = (*it)->GetUserID();

[Denis Kuznetsov (DE-MUC), 2015/06/10 16:50:46]

auto

     bool is_owner = (user_id == owner);
     bool is_public_account =
         ((*it)->GetType() == user_manager::USER_TYPE_PUBLIC_ACCOUNT);
@@ -354,8 +354,9 @@ void UserSelectionScreen::SendUserList() {
   bool single_user = users.size() == 1;
   bool is_signin_to_add = LoginDisplayHostImpl::default_host() &&
                           user_manager::UserManager::Get()->IsUserLoggedIn();
-  std::string owner;
-  chromeos::CrosSettings::Get()->GetString(chromeos::kDeviceOwner, &owner);
+  std::string owner_email;
+  chromeos::CrosSettings::Get()->GetString(chromeos::kDeviceOwner, &owner_email);
+  const user_manager::UserID owner(user_manager::UserID::FromUserEmail(owner_email));
 
   policy::BrowserPolicyConnectorChromeOS* connector =
       g_browser_process->platform_part()->browser_policy_connector_chromeos();
@@ -370,7 +371,7 @@ void UserSelectionScreen::SendUserList() {
   for (user_manager::UserList::const_iterator it = users_to_send.begin();
        it != users_to_send.end();
        ++it) {
-    const std::string& user_id = (*it)->email();
+    const user_manager::UserID& user_id = (*it)->GetUserID();
     bool is_owner = (user_id == owner);
     const bool is_public_account =
         ((*it)->GetType() == user_manager::USER_TYPE_PUBLIC_ACCOUNT);
@@ -411,7 +412,7 @@ void UserSelectionScreen::HandleGetUsers() {
   SendUserList();
 }
 
-void UserSelectionScreen::CheckUserStatus(const std::string& user_id) {
+void UserSelectionScreen::CheckUserStatus(const user_manager::UserID& user_id) {
   // No checks on lock screen.
   if (ScreenLocker::default_screen_locker())
     return;
@@ -440,7 +441,7 @@ void UserSelectionScreen::OnUserStatusChecked(
 
 // EasyUnlock stuff
 
-void UserSelectionScreen::SetAuthType(const std::string& user_id,
+void UserSelectionScreen::SetAuthType(const user_manager::UserID& user_id,
                                       AuthType auth_type,
                                       const base::string16& initial_value) {
   if (GetAuthType(user_id) == FORCE_OFFLINE_PASSWORD)
@@ -452,10 +453,10 @@ void UserSelectionScreen::SetAuthType(const std::string& user_id,
 }
 
 proximity_auth::ScreenlockBridge::LockHandler::AuthType
-UserSelectionScreen::GetAuthType(const std::string& username) const {
-  if (user_auth_type_map_.find(username) == user_auth_type_map_.end())
+UserSelectionScreen::GetAuthType(const user_manager::UserID& user_id) const {
+  if (user_auth_type_map_.find(user_id) == user_auth_type_map_.end())
     return OFFLINE_PASSWORD;
-  return user_auth_type_map_.find(username)->second;
+  return user_auth_type_map_.find(user_id)->second;
 }
 
 proximity_auth::ScreenlockBridge::LockHandler::ScreenType
@@ -474,7 +475,7 @@ void UserSelectionScreen::ShowBannerMessage(const base::string16& message) {
 }
 
 void UserSelectionScreen::ShowUserPodCustomIcon(
-    const std::string& user_id,
+    const user_manager::UserID& user_id,
     const proximity_auth::ScreenlockBridge::UserPodCustomIconOptions&
         icon_options) {
   scoped_ptr<base::DictionaryValue> icon = icon_options.ToDictionaryValue();
@@ -483,7 +484,7 @@ void UserSelectionScreen::ShowUserPodCustomIcon(
   view_->ShowUserPodCustomIcon(user_id, *icon);
 }
 
-void UserSelectionScreen::HideUserPodCustomIcon(const std::string& user_id) {
+void UserSelectionScreen::HideUserPodCustomIcon(const user_manager::UserID& user_id) {
   view_->HideUserPodCustomIcon(user_id);
 }
 
@@ -495,12 +496,12 @@ void UserSelectionScreen::EnableInput() {
     ScreenLocker::default_screen_locker()->EnableInput();
 }
 
-void UserSelectionScreen::Unlock(const std::string& user_email) {
+void UserSelectionScreen::Unlock(const user_manager::UserID& user_id) {
   DCHECK_EQ(GetScreenType(), LOCK_SCREEN);
   ScreenLocker::Hide();
 }
 
-void UserSelectionScreen::AttemptEasySignin(const std::string& user_id,
+void UserSelectionScreen::AttemptEasySignin(const user_manager::UserID& user_id,
                                             const std::string& secret,
                                             const std::string& key_label) {
   DCHECK_EQ(GetScreenType(), SIGNIN_SCREEN);
@@ -513,7 +514,7 @@ void UserSelectionScreen::AttemptEasySignin(const std::string& user_id,
   login_display_delegate_->Login(user_context, SigninSpecifics());
 }
 
-void UserSelectionScreen::HardLockPod(const std::string& user_id) {
+void UserSelectionScreen::HardLockPod(const user_manager::UserID& user_id) {
   view_->SetAuthType(user_id, OFFLINE_PASSWORD, base::string16());
   EasyUnlockService* service = GetEasyUnlockServiceForUser(user_id);
   if (!service)
@@ -521,14 +522,14 @@ void UserSelectionScreen::HardLockPod(const std::string& user_id) {
   service->SetHardlockState(EasyUnlockScreenlockStateHandler::USER_HARDLOCK);
 }
 
-void UserSelectionScreen::AttemptEasyUnlock(const std::string& user_id) {
+void UserSelectionScreen::AttemptEasyUnlock(const user_manager::UserID& user_id) {
   EasyUnlockService* service = GetEasyUnlockServiceForUser(user_id);
   if (!service)
     return;
   service->AttemptAuth(user_id);
 }
 
-void UserSelectionScreen::RecordClickOnLockIcon(const std::string& user_id) {
+void UserSelectionScreen::RecordClickOnLockIcon(const user_manager::UserID& user_id) {
   EasyUnlockService* service = GetEasyUnlockServiceForUser(user_id);
   if (!service)
     return;
@@ -536,13 +537,13 @@ void UserSelectionScreen::RecordClickOnLockIcon(const std::string& user_id) {
 }
 
 EasyUnlockService* UserSelectionScreen::GetEasyUnlockServiceForUser(
-    const std::string& user_id) const {
+    const user_manager::UserID& user_id) const {
   if (GetScreenType() == OTHER_SCREEN)
     return nullptr;
 
   const user_manager::User* unlock_user = nullptr;
   for (const user_manager::User* user : GetUsers()) {
-    if (user->email() == user_id) {
+    if (user->GetUserID() == user_id) {
       unlock_user = user;
       break;
     }