This CL replaces user_manager::UserID with AccountId.

components/user_manager/empty_user_info.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 "components/user_manager/empty_user_info.h"
 
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
+#include "components/signin/core/account_id/account_id.h"
 
 namespace user_manager {
 
 EmptyUserInfo::EmptyUserInfo() {
 }
 
 EmptyUserInfo::~EmptyUserInfo() {
 }
 
 base::string16 EmptyUserInfo::GetDisplayName() const {
   NOTIMPLEMENTED();
   return base::string16();
 }
 
 base::string16 EmptyUserInfo::GetGivenName() const {
   NOTIMPLEMENTED();
   return base::string16();
 }
 
 std::string EmptyUserInfo::GetEmail() const {
   NOTIMPLEMENTED();
   return std::string();
 }
 
-std::string EmptyUserInfo::GetUserID() const {
+AccountId EmptyUserInfo::GetUserID() const {
   NOTIMPLEMENTED();
-  return std::string();
+  return EmptyAccountId();
 }
 
 const gfx::ImageSkia& EmptyUserInfo::GetImage() const {
   NOTIMPLEMENTED();
   // To make the compiler happy.
   return null_image_;
 }
 
 }  // namespace user_manager