Add a mojo interface for AccountId

ash/common/session/session_controller_unittest.cc

 // Copyright 2016 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 "ash/common/session/session_controller.h"
 
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
@@ skipping 75 matching lines @@
   void SetSessionInfo(const mojom::SessionInfo& info) {
     mojom::SessionInfoPtr info_ptr = mojom::SessionInfo::New();
     *info_ptr = info;
     controller_->SetSessionInfo(std::move(info_ptr));
   }
 
   void UpdateSession(uint32_t session_id, const std::string& email) {
     mojom::UserSessionPtr session = mojom::UserSession::New();
     session->session_id = session_id;
     session->type = user_manager::USER_TYPE_REGULAR;
-    session->serialized_account_id =
-        AccountId::FromUserEmail(email).Serialize();
+    session->account_id = AccountId::FromUserEmail(email);
     session->display_name = email;
     session->display_email = email;
 
     controller_->UpdateUserSession(std::move(session));
   }
 
   std::string GetUserSessionEmails() const {
     std::string emails;
     for (const auto& session : controller_->GetUserSessions()) {
       emails += session->display_email + ",";
@@ skipping 120 matching lines @@
   EXPECT_EQ("user2@test.com", observer()->active_account_id().GetUserEmail());
 
   order = {1u, 2u};
   controller()->SetUserSessionOrder(order);
   EXPECT_EQ("user1@test.com,user2@test.com,", GetUserSessionEmails());
   EXPECT_EQ("user1@test.com", observer()->active_account_id().GetUserEmail());
 }
 
 }  // namespace
 }  // namespace ash