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

chrome/browser/ui/webui/chromeos/login/signin_screen_handler.h

 // Copyright (c) 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_SIGNIN_SCREEN_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_SIGNIN_SCREEN_HANDLER_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 24 matching lines @@
 #include "ui/base/ime/chromeos/input_method_manager.h"
 #include "ui/events/event_handler.h"
 
 class EasyUnlockService;
 
 namespace base {
 class DictionaryValue;
 class ListValue;
 }
 
+namespace user_manager {
+class UserID;
+} // namespace user_manager
+
 namespace chromeos {
 
 class CaptivePortalWindowProxy;
 class CoreOobeActor;
 class ErrorScreensHistogramHelper;
 class GaiaScreenHandler;
 class NativeWindowDelegate;
 class SupervisedUserCreationScreenHandler;
 class User;
 class UserContext;
@@ skipping 15 matching lines @@
 
   std::string email_;
   bool oobe_ui_;
 };
 
 // An interface for WebUILoginDisplay to call SigninScreenHandler.
 class LoginDisplayWebUIHandler {
  public:
   virtual void ClearAndEnablePassword() = 0;
   virtual void ClearUserPodPassword() = 0;
-  virtual void OnUserRemoved(const std::string& username) = 0;
+  virtual void OnUserRemoved(const user_manager::UserID& user_id) = 0;
   virtual void OnUserImageChanged(const user_manager::User& user) = 0;
   virtual void OnPreferencesChanged() = 0;
   virtual void ResetSigninScreenHandlerDelegate() = 0;
   virtual void ShowError(int login_attempts,
                          const std::string& error_text,
                          const std::string& help_link_text,
                          HelpAppLauncher::HelpTopic help_topic_id) = 0;
   virtual void ShowErrorScreen(LoginDisplay::SigninError error_id) = 0;
-  virtual void ShowGaiaPasswordChanged(const std::string& username) = 0;
-  virtual void ShowSigninUI(const std::string& email) = 0;
+  virtual void ShowGaiaPasswordChanged(const user_manager::UserID& user_id) = 0;
+  virtual void ShowSigninUI(const user_manager::UserID& user_id) = 0;
   virtual void ShowPasswordChangedDialog(bool show_password_error,
-                                         const std::string& email) = 0;
+                                         const user_manager::UserID& user_id) = 0;
   // Show sign-in screen for the given credentials.
-  virtual void ShowSigninScreenForCreds(const std::string& username,
+  virtual void ShowSigninScreenForCreds(const user_manager::UserID& user_id,
                                         const std::string& password) = 0;
   virtual void ShowWhitelistCheckFailedError() = 0;
   virtual void LoadUsers(const base::ListValue& users_list,
                          bool show_guest) = 0;
  protected:
   virtual ~LoginDisplayWebUIHandler() {}
 };
 
 // An interface for SigninScreenHandler to call WebUILoginDisplay.
 class SigninScreenHandlerDelegate {
@@ skipping 51 matching lines @@
 
   // Sets the displayed email for the next login attempt. If it succeeds,
   // user's displayed email value will be updated to |email|.
   virtual void SetDisplayEmail(const std::string& email) = 0;
 
   // --------------- Rest of the methods.
   // Cancels user adding.
   virtual void CancelUserAdding() = 0;
 
   // Load wallpaper for given |username|.
-  virtual void LoadWallpaper(const std::string& username) = 0;
+  virtual void LoadWallpaper(const user_manager::UserID& user_id) = 0;
 
   // Loads the default sign-in wallpaper.
   virtual void LoadSigninWallpaper() = 0;
 
   // Attempts to remove given user.
-  virtual void RemoveUser(const std::string& username) = 0;
+  virtual void RemoveUser(const user_manager::UserID& user_id) = 0;
 
   // Let the delegate know about the handler it is supposed to be using.
   virtual void SetWebUIHandler(LoginDisplayWebUIHandler* webui_handler) = 0;
 
   // Returns users list to be shown.
   virtual const user_manager::UserList& GetUsers() const = 0;
 
   // Whether login as guest is available.
   virtual bool IsShowGuest() const = 0;
 
   // Weather to show the user pods or only GAIA sign in.
   // Public sessions are always shown.
   virtual bool IsShowUsers() const = 0;
 
   // Whether user sign in has completed.
   virtual bool IsUserSigninCompleted() const = 0;
 
   // Request to (re)load user list.
   virtual void HandleGetUsers() = 0;
 
   // Runs an OAuth token validation check for user.
-  virtual void CheckUserStatus(const std::string& user_id) = 0;
+  virtual void CheckUserStatus(const user_manager::UserID& user_id) = 0;
 
  protected:
   virtual ~SigninScreenHandlerDelegate() {}
 };
 
 // A class that handles the WebUI hooks in sign-in screen in OobeDisplay
 // and LoginDisplay.
 class SigninScreenHandler
     : public BaseScreenHandler,
       public LoginDisplayWebUIHandler,
       public content::NotificationObserver,
       public NetworkStateInformer::NetworkStateInformerObserver,
       public input_method::ImeKeyboard::Observer,
       public TouchViewControllerDelegate::Observer,
       public OobeUI::Observer {
  public:
   SigninScreenHandler(
       const scoped_refptr<NetworkStateInformer>& network_state_informer,
       NetworkErrorModel* network_error_model,
       CoreOobeActor* core_oobe_actor,
       GaiaScreenHandler* gaia_screen_handler);
   ~SigninScreenHandler() override;
 
-  static std::string GetUserLRUInputMethod(const std::string& username);
+  static std::string GetUserLRUInputMethod(const user_manager::UserID& user_id);
 
   // Update current input method (namely keyboard layout) in the given IME state
   // to LRU by this user.
   static void SetUserInputMethod(
-      const std::string& username,
+      const user_manager::UserID& user_id,
       input_method::InputMethodManager::State* ime_state);
 
   // Shows the sign in screen.
   void Show(const LoginScreenContext& context);
 
   // Sets delegate to be used by the handler. It is guaranteed that valid
   // delegate is set before Show() method will be called.
   void SetDelegate(SigninScreenHandlerDelegate* delegate);
 
   void SetNativeWindowDelegate(NativeWindowDelegate* native_window_delegate);
@@ skipping 47 matching lines @@
       ::login::LocalizedValuesBuilder* builder) override;
   void Initialize() override;
   gfx::NativeWindow GetNativeWindow() override;
 
   // WebUIMessageHandler implementation:
   void RegisterMessages() override;
 
   // LoginDisplayWebUIHandler implementation:
   void ClearAndEnablePassword() override;
   void ClearUserPodPassword() override;
-  void OnUserRemoved(const std::string& username) override;
+  void OnUserRemoved(const user_manager::UserID& user_id) override;
   void OnUserImageChanged(const user_manager::User& user) override;
   void OnPreferencesChanged() override;
   void ResetSigninScreenHandlerDelegate() override;
   void ShowError(int login_attempts,
                  const std::string& error_text,
                  const std::string& help_link_text,
                  HelpAppLauncher::HelpTopic help_topic_id) override;
-  void ShowGaiaPasswordChanged(const std::string& username) override;
-  void ShowSigninUI(const std::string& email) override;
+  void ShowGaiaPasswordChanged(const user_manager::UserID& user_id) override;
+  void ShowSigninUI(const user_manager::UserID& user_id) override;
   void ShowPasswordChangedDialog(bool show_password_error,
-                                 const std::string& email) override;
+                                 const user_manager::UserID& user_id) override;
   void ShowErrorScreen(LoginDisplay::SigninError error_id) override;
-  void ShowSigninScreenForCreds(const std::string& username,
+  void ShowSigninScreenForCreds(const user_manager::UserID& user_id,
                                 const std::string& password) override;
   void ShowWhitelistCheckFailedError() override;
   void LoadUsers(const base::ListValue& users_list, bool show_guest) override;
 
   // content::NotificationObserver implementation:
   void Observe(int type,
                const content::NotificationSource& source,
                const content::NotificationDetails& details) override;
 
   // TouchViewControllerDelegate::Observer implementation:
@@ skipping 51 matching lines @@
                                              const std::string& locale);
   void HandleCancelConsumerManagementEnrollment();
   void HandleGetTouchViewState();
   void HandleLogRemoveUserWarningShown();
   void HandleFirstIncorrectPasswordAttempt(const std::string& email);
   void HandleMaxIncorrectPasswordAttempts(const std::string& email);
 
   // Sends the list of |keyboard_layouts| available for the |locale| that is
   // currently selected for the public session identified by |user_id|.
   void SendPublicSessionKeyboardLayouts(
-      const std::string& user_id,
+      const user_manager::UserID& user_id,
       const std::string& locale,
       scoped_ptr<base::ListValue> keyboard_layouts);
 
   // Returns true iff
   // (i)   log in is restricted to some user list,
   // (ii)  all users in the restricted list are present.
   bool AllWhitelistedUsersPresent();
 
   // Cancels password changed flow - switches back to login screen.
   // Called as a callback after cookies are cleared.
@@ skipping 28 matching lines @@
 
   // input_method::ImeKeyboard::Observer implementation:
   void OnCapsLockChanged(bool enabled) override;
 
   // Returns OobeUI object of NULL.
   OobeUI* GetOobeUI() const;
 
   // Gets the easy unlock service associated with the user. Can return NULL if
   // user cannot be found, or there is not associated service.
   EasyUnlockService* GetEasyUnlockServiceForUser(
-      const std::string& username) const;
+      const user_manager::UserID& user_id) const;
 
   // Current UI state of the signin screen.
   UIState ui_state_ = UI_STATE_UNKNOWN;
 
   // A delegate that glues this handler with backend LoginDisplay.
   SigninScreenHandlerDelegate* delegate_ = nullptr;
 
   // A delegate used to get gfx::NativeWindow.
   NativeWindowDelegate* native_window_delegate_ = nullptr;
 
@@ skipping 60 matching lines @@
   scoped_ptr<ErrorScreensHistogramHelper> histogram_helper_;
 
   base::WeakPtrFactory<SigninScreenHandler> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SigninScreenHandler);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_UI_WEBUI_CHROMEOS_LOGIN_SIGNIN_SCREEN_HANDLER_H_