This CL replaces e-mail with AccountId on user selection screen.

components/user_manager/user_info_impl.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 COMPONENTS_USER_MANAGER_USER_INFO_IMPL_H_
 #define COMPONENTS_USER_MANAGER_USER_INFO_IMPL_H_
 
 #include <string>
 
 #include "base/strings/string16.h"
+#include "components/signin/core/account_id/account_id.h"
 #include "components/user_manager/user_info.h"
 #include "components/user_manager/user_manager_export.h"
 #include "ui/gfx/image/image_skia.h"
 
 namespace user_manager {
 
 // Stub implementation of UserInfo interface. Used in tests.
 class USER_MANAGER_EXPORT UserInfoImpl : public UserInfo {
  public:
   UserInfoImpl();
   ~UserInfoImpl() override;
 
   // UserInfo:
   base::string16 GetDisplayName() const override;
   base::string16 GetGivenName() const override;
   std::string GetEmail() const override;
-  AccountId GetAccountId() const override;
+  const AccountId& GetAccountId() const override;
   const gfx::ImageSkia& GetImage() const override;
 
  private:
+  const AccountId account_id_;
   gfx::ImageSkia user_image_;
 
   DISALLOW_COPY_AND_ASSIGN(UserInfoImpl);
 };
 
 }  // namespace user_manager
 
 #endif  // COMPONENTS_USER_MANAGER_USER_INFO_IMPL_H_