Finish decoupling sync and invalidations

sync/internal_api/public/base/ack_handle.h

-// Copyright 2013 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 SYNC_INTERNAL_API_PUBLIC_BASE_ACK_HANDLE_H
-#define SYNC_INTERNAL_API_PUBLIC_BASE_ACK_HANDLE_H
-
-#include <string>
-
-#include "base/basictypes.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/time/time.h"
-#include "sync/base/sync_export.h"
-
-namespace base {
-class DictionaryValue;
-}
-
-namespace syncer {
-
-// Opaque class that represents a local ack handle. We don't reuse the
-// invalidation ack handles to avoid unnecessary dependencies.
-class SYNC_EXPORT AckHandle {
- public:
-  static AckHandle CreateUnique();
-  static AckHandle InvalidAckHandle();
-
-  bool Equals(const AckHandle& other) const;
-
-  scoped_ptr<base::DictionaryValue> ToValue() const;
-  bool ResetFromValue(const base::DictionaryValue& value);
-
-  bool IsValid() const;
-
-  ~AckHandle();
-
- private:
-  // Explicitly copyable and assignable for STL containers.
-  AckHandle(const std::string& state, base::Time timestamp);
-
-  std::string state_;
-  base::Time timestamp_;
-};
-
-}  // namespace syncer
-
-#endif  // SYNC_INTERNAL_API_PUBLIC_BASE_ACK_HANDLE_H