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

blimp/helium/revision_generator.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_REVISION_GENERATOR_H_
-#define BLIMP_HELIUM_REVISION_GENERATOR_H_
-
-#include "base/lazy_instance.h"
-#include "base/macros.h"
-#include "base/sequence_checker.h"
-#include "blimp/helium/blimp_helium_export.h"
-#include "blimp/helium/version_vector.h"
-
-namespace blimp {
-namespace helium {
-
-// Responsible for generating monotonically increasing values
-// of Revisions. This generator is used one per host
-// (client or engine) to ensure they have a single clock domain.
-class BLIMP_HELIUM_EXPORT RevisionGenerator {
- public:
-  RevisionGenerator() = default;
-
-  const Revision& current() { return revision_; }
-
-  const Revision& GetNextRevision();
-
-  static RevisionGenerator* GetInstance();
-
- private:
-  static base::LazyInstance<RevisionGenerator> instance_;
-
-  Revision revision_ = 0;
-  base::SequenceChecker sequence_checker_;
-
-  DISALLOW_COPY_AND_ASSIGN(RevisionGenerator);
-};
-
-Revision BLIMP_HELIUM_EXPORT GetNextRevision();
-
-}  // namespace helium
-}  // namespace blimp
-
-#endif  // BLIMP_HELIUM_REVISION_GENERATOR_H_