Show different error message if ARC is disabled.

chrome/browser/chromeos/arc/auth/arc_background_auth_code_fetcher.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 "chrome/browser/chromeos/arc/auth/arc_background_auth_code_fetcher.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
@@ skipping 164 matching lines @@
 
 void ArcBackgroundAuthCodeFetcher::ResetFetchers() {
   login_token_request_.reset();
   auth_code_fetcher_.reset();
 }
 
 void ArcBackgroundAuthCodeFetcher::ReportResult(
     const std::string& auth_code,
     OptInSilentAuthCode uma_status) {
   UpdateSilentAuthCodeUMA(uma_status);
-  base::ResetAndReturn(&callback_).Run(auth_code);
+  base::ResetAndReturn(&callback_)
+      .Run(auth_code.empty() ? ArcAuthInfoFetcher::Status::FAILURE
+                             : ArcAuthInfoFetcher::Status::SUCCESS,
+           auth_code);
 }
 
 }  // namespace arc