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

chromeos/dbus/fake_session_manager_client.h

 // 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.
 
 #ifndef CHROMEOS_DBUS_FAKE_SESSION_MANAGER_CLIENT_H_
 #define CHROMEOS_DBUS_FAKE_SESSION_MANAGER_CLIENT_H_
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/observer_list.h"
 #include "chromeos/dbus/session_manager_client.h"
+#include "components/user_manager/user_id.h"
 
 namespace chromeos {
 
 // A fake implementation of session_manager. Accepts policy blobs to be set and
 // returns them unmodified.
 class FakeSessionManagerClient : public SessionManagerClient {
  public:
   FakeSessionManagerClient();
   ~FakeSessionManagerClient() override;
 
   // SessionManagerClient overrides
   void Init(dbus::Bus* bus) override;
   void SetStubDelegate(StubDelegate* delegate) override;
   void AddObserver(Observer* observer) override;
   void RemoveObserver(Observer* observer) override;
   bool HasObserver(const Observer* observer) const override;
   bool IsScreenLocked() const override;
   void EmitLoginPromptVisible() override;
   void RestartJob(int pid, const std::string& command_line) override;
-  void StartSession(const std::string& user_email) override;
+  void StartSession(const user_manager::UserID& user_id) override;
   void StopSession() override;
   void NotifySupervisedUserCreationStarted() override;
   void NotifySupervisedUserCreationFinished() override;
   void StartDeviceWipe() override;
   void RequestLockScreen() override;
   void NotifyLockScreenShown() override;
   void NotifyLockScreenDismissed() override;
   void RetrieveActiveSessions(const ActiveSessionsCallback& callback) override;
   void RetrieveDevicePolicy(const RetrievePolicyCallback& callback) override;
-  void RetrievePolicyForUser(const std::string& username,
+  void RetrievePolicyForUser(const user_manager::UserID& user_id,
                              const RetrievePolicyCallback& callback) override;
   std::string BlockingRetrievePolicyForUser(
-      const std::string& username) override;
+      const user_manager::UserID& user_id) override;
   void RetrieveDeviceLocalAccountPolicy(
       const std::string& account_id,
       const RetrievePolicyCallback& callback) override;
   void StoreDevicePolicy(const std::string& policy_blob,
                          const StorePolicyCallback& callback) override;
-  void StorePolicyForUser(const std::string& username,
+  void StorePolicyForUser(const user_manager::UserID& user_id,
                           const std::string& policy_blob,
                           const StorePolicyCallback& callback) override;
   void StoreDeviceLocalAccountPolicy(
       const std::string& account_id,
       const std::string& policy_blob,
       const StorePolicyCallback& callback) override;
-  void SetFlagsForUser(const std::string& username,
+  void SetFlagsForUser(const user_manager::UserID& user_id,
                        const std::vector<std::string>& flags) override;
   void GetServerBackedStateKeys(const StateKeysCallback& callback) override;
 
   const std::string& device_policy() const;
   void set_device_policy(const std::string& policy_blob);
 
-  const std::string& user_policy(const std::string& username) const;
-  void set_user_policy(const std::string& username,
+  const std::string& user_policy(const user_manager::UserID& user_id) const;
+  void set_user_policy(const user_manager::UserID& user_id,
                        const std::string& policy_blob);
 
   const std::string& device_local_account_policy(
       const std::string& account_id) const;
   void set_device_local_account_policy(const std::string& account_id,
                                        const std::string& policy_blob);
 
   // Notify observers about a property change completion.
   void OnPropertyChangeComplete(bool success);
 
@@ skipping 13 matching lines @@
     return notify_lock_screen_shown_call_count_;
   }
 
   // Returns how many times LockScreenDismissed() was called.
   int notify_lock_screen_dismissed_call_count() const {
     return notify_lock_screen_dismissed_call_count_;
   }
 
  private:
   std::string device_policy_;
-  std::map<std::string, std::string> user_policies_;
+  std::map<user_manager::UserID, std::string> user_policies_;
   std::map<std::string, std::string> device_local_account_policy_;
   ObserverList<Observer> observers_;
   SessionManagerClient::ActiveSessionsMap user_sessions_;
   std::vector<std::string> server_backed_state_keys_;
 
   int start_device_wipe_call_count_;
   int notify_lock_screen_shown_call_count_;
   int notify_lock_screen_dismissed_call_count_;
 
   DISALLOW_COPY_AND_ASSIGN(FakeSessionManagerClient);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DBUS_FAKE_SESSION_MANAGER_CLIENT_H_