ARC: Fix auth_code UMA stats

Add missing else in if-else statement in HTTP error handling

Change-Id: I1da56170c43948af598a03ac9876f4a9ba257196
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2151510Reviewed-by: Yury Khmel <khmel@chromium.org>
Reviewed-by: Kush Sinha <sinhak@chromium.org>
Commit-Queue: Andrei Salavei <solovey@google.com>
Cr-Commit-Position: refs/heads/master@{#759974}

chrome/browser/chromeos/arc/auth/arc_background_auth_code_fetcher.cc

@@ -184,7 +184,7 @@ void ArcBackgroundAuthCodeFetcher::OnSimpleLoaderComplete(
     OptInSilentAuthCode uma_status;
     if (response_code >= 400 && response_code < 500)
       uma_status = OptInSilentAuthCode::HTTP_CLIENT_FAILURE;
-    if (response_code >= 500 && response_code < 600)
+    else if (response_code >= 500 && response_code < 600)
       uma_status = OptInSilentAuthCode::HTTP_SERVER_FAILURE;
     else
       uma_status = OptInSilentAuthCode::HTTP_UNKNOWN_FAILURE;