Revert of [Sync] IWYU cleanup.

components/sync/engine/attachments/on_disk_attachment_store.cc

 // 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.
 
 #include "components/sync/engine/attachments/on_disk_attachment_store.h"
 
 #include <stdint.h>
 
+#include <memory>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/location.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/sequenced_task_runner.h"
 #include "components/sync/engine/attachments/attachment_util.h"
 #include "components/sync/engine_impl/attachments/proto/attachment_store.pb.h"
@@ skipping 512 matching lines @@
   return key;
 }
 
 AttachmentMetadata OnDiskAttachmentStore::MakeAttachmentMetadata(
     const AttachmentId& attachment_id,
     const attachment_store_pb::RecordMetadata& record_metadata) {
   return AttachmentMetadata(attachment_id, record_metadata.attachment_size());
 }
 
 }  // namespace syncer