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

chrome/browser/extensions/api/easy_unlock_private/easy_unlock_private_api.cc

 // 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.
 
 #include "chrome/browser/extensions/api/easy_unlock_private/easy_unlock_private_api.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 624 matching lines @@
   const std::string challenge =
       EasyUnlockService::Get(profile)->GetChallenge();
   if (!challenge.empty() && !params->nonce.empty()) {
     EasyUnlockTpmKeyManager* key_manager =
         EasyUnlockTpmKeyManagerFactory::GetInstance()->Get(profile);
     if (!key_manager) {
       SetError("No EasyUnlockTpmKeyManager.");
       return false;
     }
     key_manager->SignUsingTpmKey(
-        EasyUnlockService::Get(profile)->GetUserEmail(),
+        EasyUnlockService::Get(profile)->GetUserID(),
         std::string(params->nonce.begin(), params->nonce.end()),
         base::Bind(&EasyUnlockPrivateGetSignInChallengeFunction::OnDone, this,
                    challenge));
   } else {
     OnDone(challenge, std::string());
   }
   return true;
 #else  // if !defined(OS_CHROMEOS)
   SetError("Sign-in not supported.");
   return false;
@@ skipping 31 matching lines @@
 EasyUnlockPrivateGetUserInfoFunction::EasyUnlockPrivateGetUserInfoFunction() {
 }
 
 EasyUnlockPrivateGetUserInfoFunction::~EasyUnlockPrivateGetUserInfoFunction() {
 }
 
 bool EasyUnlockPrivateGetUserInfoFunction::RunSync() {
   EasyUnlockService* service =
       EasyUnlockService::Get(Profile::FromBrowserContext(browser_context()));
   std::vector<linked_ptr<easy_unlock_private::UserInfo> > users;
-  std::string user_id = service->GetUserEmail();
+  user_manager::UserID user_id = service->GetUserID();
   if (!user_id.empty()) {
     users.push_back(
         linked_ptr<easy_unlock_private::UserInfo>(
             new easy_unlock_private::UserInfo()));
     users[0]->user_id = user_id;
     users[0]->logged_in = service->GetType() == EasyUnlockService::TYPE_REGULAR;
     users[0]->data_ready = users[0]->logged_in ||
                            service->GetRemoteDevices() != NULL;
 
     EasyUnlockService::UserSettings user_settings =
@@ skipping 128 matching lines @@
     error_message = *params->result.error_message;
 
   Profile* profile = Profile::FromBrowserContext(browser_context());
   EasyUnlockService::Get(profile)
       ->SetAutoPairingResult(params->result.success, error_message);
 
   return true;
 }
 
 }  // namespace extensions