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

chrome/browser/signin/easy_unlock_service_regular.h

 // 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.
 
 #ifndef CHROME_BROWSER_SIGNIN_EASY_UNLOCK_SERVICE_REGULAR_H_
 #define CHROME_BROWSER_SIGNIN_EASY_UNLOCK_SERVICE_REGULAR_H_
 
 #include <string>
 
 #include "base/callback.h"
@@ skipping 14 matching lines @@
 }
 
 namespace cryptauth {
 class ToggleEasyUnlockResponse;
 }
 
 namespace proximity_auth {
 class CryptAuthClient;
 }
 
+namespace user_manager {
+class UserID;
+}
+
 class EasyUnlockAppManager;
 class EasyUnlockToggleFlow;
 class Profile;
 
 // EasyUnlockService instance that should be used for regular, non-signin
 // profiles.
 class EasyUnlockServiceRegular
     : public EasyUnlockService,
       public proximity_auth::ScreenlockBridge::Observer {
  public:
   explicit EasyUnlockServiceRegular(Profile* profile);
   ~EasyUnlockServiceRegular() override;
 
  private:
   // EasyUnlockService implementation:
   EasyUnlockService::Type GetType() const override;
-  std::string GetUserEmail() const override;
+  user_manager::UserID GetUserID() const override;
   void LaunchSetup() override;
   const base::DictionaryValue* GetPermitAccess() const override;
   void SetPermitAccess(const base::DictionaryValue& permit) override;
   void ClearPermitAccess() override;
   const base::ListValue* GetRemoteDevices() const override;
   void SetRemoteDevices(const base::ListValue& devices) override;
   void RunTurnOffFlow() override;
   void ResetTurnOffFlow() override;
   TurnOffFlowStatus GetTurnOffFlowStatus() const override;
   std::string GetChallenge() const override;
   std::string GetWrappedSecret() const override;
-  void RecordEasySignInOutcome(const std::string& user_id,
+  void RecordEasySignInOutcome(const user_manager::UserID& user_id,
                                bool success) const override;
-  void RecordPasswordLoginEvent(const std::string& user_id) const override;
+  void RecordPasswordLoginEvent(const user_manager::UserID& user_id) const override;
   void StartAutoPairing(const AutoPairingResultCallback& callback) override;
   void SetAutoPairingResult(bool success, const std::string& error) override;
   void InitializeInternal() override;
   void ShutdownInternal() override;
   bool IsAllowedInternal() const override;
   void OnWillFinalizeUnlock(bool success) override;
   void OnSuspendDone() override;
 
   // proximity_auth::ScreenlockBridge::Observer implementation:
   void OnScreenDidLock(proximity_auth::ScreenlockBridge::LockHandler::ScreenType
                            screen_type) override;
   void OnScreenDidUnlock(
       proximity_auth::ScreenlockBridge::LockHandler::ScreenType screen_type)
       override;
-  void OnFocusedUserChanged(const std::string& user_id) override;
+  void OnFocusedUserChanged(const user_manager::UserID& user_id) override;
 
+  // Returns email of the user currently associated with the service.
+  std::string GetUserEmail() const;
 
   // Callback when the controlling pref changes.
   void OnPrefsChanged();
 
   // Sets the new turn-off flow status.
   void SetTurnOffFlowStatus(TurnOffFlowStatus status);
 
   // Callback for ToggleEasyUnlock CryptAuth API.
   void OnToggleEasyUnlockApiComplete(
       const cryptauth::ToggleEasyUnlockResponse& response);
@@ skipping 34 matching lines @@
   // sleep -- e.g. by opening the lid -- but can also be shown if the screen is
   // locked but the computer does not go to sleep.
   base::TimeTicks lock_screen_last_shown_timestamp_;
 
   base::WeakPtrFactory<EasyUnlockServiceRegular> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(EasyUnlockServiceRegular);
 };
 
 #endif  // CHROME_BROWSER_SIGNIN_EASY_UNLOCK_SERVICE_REGULAR_H_