[Sync] Removing duplicated includes between cc and h files.

components/sync/api/attachments/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/api/attachments/attachment_store.h"
 
 #include <utility>
 
 #include "base/bind.h"
-#include "base/callback.h"
 #include "base/location.h"
 #include "base/message_loop/message_loop.h"
 #include "base/sequenced_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/sync/core/attachments/attachment_store_frontend.h"
 #include "components/sync/core/attachments/in_memory_attachment_store.h"
 #include "components/sync/core/attachments/on_disk_attachment_store.h"
 
 namespace syncer {
 
@@ skipping 109 matching lines @@
   frontend()->DropReference(sync_component_, ids,
                             base::Bind(&NoOpDropCallback));
 }
 
 void AttachmentStoreForSync::ReadMetadataForSync(
     const ReadMetadataCallback& callback) {
   frontend()->ReadMetadata(sync_component_, callback);
 }
 
 }  // namespace syncer