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

chromeos/tpm/tpm_token_info_getter.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 CHROMEOS_TPM_TPM_TOKEN_INFO_GETTER_H_
 #define CHROMEOS_TPM_TPM_TOKEN_INFO_GETTER_H_
 
 #include <string>
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
 #include "chromeos/chromeos_export.h"
 #include "chromeos/dbus/dbus_method_call_status.h"
+#include "components/user_manager/user_id.h"
 
 namespace base {
 class TaskRunner;
 }
 
 namespace chromeos {
 class CryptohomeClient;
 }
 
 namespace chromeos {
@@ skipping 13 matching lines @@
 };
 
 // Class for getting a user or the system TPM token info from cryptohome during
 // TPM token loading.
 class CHROMEOS_EXPORT TPMTokenInfoGetter {
  public:
   using TPMTokenInfoCallback = base::Callback<void(const TPMTokenInfo& info)>;
 
   // Factory method for TPMTokenInfoGetter for a user token.
   static scoped_ptr<TPMTokenInfoGetter> CreateForUserToken(
-      const std::string& user_id,
+      const user_manager::UserID& user_id,
       CryptohomeClient* cryptohome_client,
       const scoped_refptr<base::TaskRunner>& delayed_task_runner);
 
   // Factory method for TPMTokenGetter for the system token.
   static scoped_ptr<TPMTokenInfoGetter> CreateForSystemToken(
       CryptohomeClient* cryptohome_client,
       const scoped_refptr<base::TaskRunner>& delayed_task_runner);
 
   ~TPMTokenInfoGetter();
 
@@ skipping 12 matching lines @@
 
   enum State {
     STATE_INITIAL,
     STATE_STARTED,
     STATE_TPM_ENABLED,
     STATE_DONE
   };
 
   TPMTokenInfoGetter(
       Type type,
-      const std::string& user_id,
+      const user_manager::UserID& user_id,
       CryptohomeClient* cryptohome_client,
       const scoped_refptr<base::TaskRunner>& delayed_task_runner);
 
   // Continues TPM token info getting procedure by starting the task associated
   // with the current TPMTokenInfoGetter state.
   void Continue();
 
   // If token initialization step fails (e.g. if tpm token is not yet ready)
   // schedules the initialization step retry attempt after a timeout.
   void RetryLater();
 
   // Cryptohome methods callbacks.
   void OnTpmIsEnabled(DBusMethodCallStatus call_status,
                       bool tpm_is_enabled);
   void OnPkcs11GetTpmTokenInfo(DBusMethodCallStatus call_status,
                                const std::string& token_name,
                                const std::string& user_pin,
                                int token_slot_id);
 
   // The task runner used to run delayed tasks when retrying failed Cryptohome
   // calls.
   scoped_refptr<base::TaskRunner> delayed_task_runner_;
 
   Type type_;
   State state_;
 
   // The user id associated with the TPMTokenInfoGetter. Empty for system token.
-  std::string user_id_;
+  user_manager::UserID user_id_;
 
   TPMTokenInfoCallback callback_;
 
   // The current request delay before the next attempt to initialize the
   // TPM. Will be adapted after each attempt.
   base::TimeDelta tpm_request_delay_;
 
   CryptohomeClient* cryptohome_client_;
 
   base::WeakPtrFactory<TPMTokenInfoGetter> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TPMTokenInfoGetter);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_TPM_TPM_TOKEN_INFO_GETTER_H_