Delete blimp/helium and remove references to it from dependent targets

blimp/helium/syncable_common.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 BLIMP_HELIUM_SYNCABLE_COMMON_H_
-#define BLIMP_HELIUM_SYNCABLE_COMMON_H_
-
-#include "blimp/helium/blimp_helium_export.h"
-
-namespace blimp {
-namespace helium {
-
-enum class Peer { CLIENT, ENGINE };
-
-enum class Bias { LOCAL, REMOTE };
-
-// Determines whether a Syncable should be biased toward local or remote
-// mutations in the event of a conflict.
-Bias BLIMP_HELIUM_EXPORT ComputeBias(Peer owner, Peer running_as);
-
-}  // namespace helium
-}  // namespace blimp
-
-#endif  // BLIMP_HELIUM_SYNCABLE_COMMON_H_