[Sync] Move the last things out of core/.

components/sync/core_impl/protocol_event_buffer.h

-// Copyright 2014 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 COMPONENTS_SYNC_CORE_IMPL_PROTOCOL_EVENT_BUFFER_H_
-#define COMPONENTS_SYNC_CORE_IMPL_PROTOCOL_EVENT_BUFFER_H_
-
-#include <stddef.h>
-
-#include <deque>
-#include <memory>
-#include <vector>
-
-#include "base/macros.h"
-
-namespace syncer {
-
-class ProtocolEvent;
-
-// A container for ProtocolEvents.
-//
-// Stores at most kBufferSize events, then starts dropping the oldest events.
-class ProtocolEventBuffer {
- public:
-  static const size_t kBufferSize;
-
-  ProtocolEventBuffer();
-  ~ProtocolEventBuffer();
-
-  // Records an event.  May cause the oldest event to be dropped.
-  void RecordProtocolEvent(const ProtocolEvent& event);
-
-  // Returns copies of the buffered contents.  Will not clear the buffer.
-  std::vector<std::unique_ptr<ProtocolEvent>> GetBufferedProtocolEvents() const;
-
- private:
-  std::deque<std::unique_ptr<ProtocolEvent>> buffer_;
-
-  DISALLOW_COPY_AND_ASSIGN(ProtocolEventBuffer);
-};
-
-}  // namespace syncer
-
-#endif  // COMPONENTS_SYNC_CORE_IMPL_PROTOCOL_EVENT_BUFFER_H_