Make it possible to build without enable_supervised_users.

chrome/browser/sync/supervised_user_signin_manager_wrapper.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 CHROME_BROWSER_SYNC_SUPERVISED_USER_SIGNIN_MANAGER_WRAPPER_H_
 #define CHROME_BROWSER_SYNC_SUPERVISED_USER_SIGNIN_MANAGER_WRAPPER_H_
 
 #include <string>
 
 #include "base/macros.h"
+#include "chrome/browser/supervised_user/supervised_users.h"
 #include "components/sync/driver/signin_manager_wrapper.h"
 
 class Profile;
 class SigninManagerBase;
 
 // Some chrome cloud services support supervised users as well as normally
 // authenticated users that sign in through SigninManager.  To facilitate
 // getting the "effective" username and account identifiers, services can
 // use this class to wrap the SigninManager and return supervised user account
 // information when appropriate.
 class SupervisedUserSigninManagerWrapper : public SigninManagerWrapper {
  public:
   SupervisedUserSigninManagerWrapper(Profile* profile,
                                      SigninManagerBase* original);
   ~SupervisedUserSigninManagerWrapper() override;
 
   // SigninManagerWrapper implementation
   std::string GetEffectiveUsername() const override;
   std::string GetAccountIdToUse() const override;
   std::string GetSyncScopeToUse() const override;
 
  private:
   Profile* profile_;
 
   DISALLOW_COPY_AND_ASSIGN(SupervisedUserSigninManagerWrapper);
 };
 
 #endif  // CHROME_BROWSER_SYNC_SUPERVISED_USER_SIGNIN_MANAGER_WRAPPER_H_