Move session service and supervised users to buildflags.

chrome/browser/ui/webui/signin/md_user_manager_ui.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_SIGNIN_MD_USER_MANAGER_UI_H_
 #define CHROME_BROWSER_UI_WEBUI_SIGNIN_MD_USER_MANAGER_UI_H_
 
 #include "base/macros.h"
+#include "chrome/common/features.h"
 #include "content/public/browser/web_ui_controller.h"
 
 class SigninCreateProfileHandler;
 class UserManagerScreenHandler;
 
-#if defined(ENABLE_SUPERVISED_USERS)
+#if BUILDFLAG(ENABLE_SUPERVISED_USERS)
 class SigninSupervisedUserImportHandler;
 #endif
 
 namespace base {
 class DictionaryValue;
 }
 namespace content {
 class WebUIDataSource;
 }
 
 // A WebUI dialog to display available users.
 class MDUserManagerUI : public content::WebUIController {
  public:
   explicit MDUserManagerUI(content::WebUI* web_ui);
   ~MDUserManagerUI() override;
 
  private:
   content::WebUIDataSource* CreateUIDataSource(
       const base::DictionaryValue& localized_strings);
   void GetLocalizedStrings(base::DictionaryValue* localized_strings);
 
   SigninCreateProfileHandler* signin_create_profile_handler_;
   UserManagerScreenHandler* user_manager_screen_handler_;
 
-#if defined(ENABLE_SUPERVISED_USERS)
+#if BUILDFLAG(ENABLE_SUPERVISED_USERS)
   SigninSupervisedUserImportHandler* signin_supervised_user_import_handler_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(MDUserManagerUI);
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SIGNIN_MD_USER_MANAGER_UI_H_