Show different error message if ARC is disabled.

chrome/browser/chromeos/arc/auth/arc_auth_info_fetcher.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_CHROMEOS_ARC_AUTH_ARC_AUTH_INFO_FETCHER_H_
 #define CHROME_BROWSER_CHROMEOS_ARC_AUTH_ARC_AUTH_INFO_FETCHER_H_
 
 #include <string>
 
 #include "base/callback.h"
 
 namespace arc {
 
+enum class ArcAuthInfoFetchStatus {
+  SUCCESS,       // The fetch was successful.
+  FAILURE,       // The request failed.
+  ARC_DISABLED,  // ARC is not enabled.
+  SIZE,          // The size of this enum; keep last.

[Luis Héctor Chávez, 2017/02/21 19:32:11]

Do you *need* the SIZE? Seems like you're only using this in tests and not for
UMA purposes, so you should be able to remove it and also remove all default:
labels in all the switch blocks where you use ArcAuthInfoFetchStatus, that way
the compiler will complain if you are not being exhaustive in the switch.

Also, how about moving this enum into ArcAuthInfoFetcher? That way it will be
ArcAuthInfoFetcher::Status :)

[Marton Hunyady, 2017/02/22 16:07:54]

Done. (This also means I can't forward declare it in arc_auth_service.h)

+};
+
 // Interface to implement auth_code or enrollment token fetching.
 class ArcAuthInfoFetcher {
  public:
   virtual ~ArcAuthInfoFetcher() = default;
 
-  // Fetches the auth code or the enrollment token. On success, |callback| is
-  // called with the fetched |auth_info|. Otherwise, |callback| is called with
-  // empty string.
+  // Fetches the auth code or the enrollment token.
+  // On success, |callback| is called with status = SUCCESS and with the fetched

[Luis Héctor Chávez, 2017/02/21 19:32:11]

nit: "|status|". Same below.

[Marton Hunyady, 2017/02/22 16:07:54]

Done.

+  // |auth_info|. Otherwise, status contains the reason of the failure.
   // Fetch() should be called once per instance, and it is expected that
   // the inflight operation is cancelled without calling the |callback|
   // when the instance is deleted.
-  using FetchCallback = base::Callback<void(const std::string& auth_info)>;
+  using FetchCallback = base::Callback<void(ArcAuthInfoFetchStatus status,
+                                            const std::string& auth_info)>;
   virtual void Fetch(const FetchCallback& callback) = 0;
 };
 
 }  // namespace arc
 
 #endif  // CHROME_BROWSER_CHROMEOS_ARC_AUTH_ARC_AUTH_INFO_FETCHER_H_