[Sync] Move attachments code out of core/.

components/sync/core/attachments/attachment_service.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_ATTACHMENTS_ATTACHMENT_SERVICE_H_
-#define COMPONENTS_SYNC_CORE_ATTACHMENTS_ATTACHMENT_SERVICE_H_
-
-#include <memory>
-
-#include "base/callback.h"
-#include "base/memory/weak_ptr.h"
-#include "components/sync/api/attachments/attachment.h"
-
-namespace syncer {
-
-class AttachmentStore;
-class SyncData;
-
-// AttachmentService is responsible for managing a model type's attachments.
-//
-// Outside of sync code, AttachmentService shouldn't be used directly. Instead
-// use the functionality provided by SyncData and SyncChangeProcessor.
-//
-// Destroying this object does not necessarily cancel outstanding async
-// operations. If you need cancel like semantics, use WeakPtr in the callbacks.
-class AttachmentService {
- public:
-  // The result of a GetOrDownloadAttachments operation.
-  enum GetOrDownloadResult {
-    GET_SUCCESS,            // No error, all attachments returned.
-    GET_UNSPECIFIED_ERROR,  // An unspecified error occurred.
-  };
-
-  typedef base::Callback<void(const GetOrDownloadResult&,
-                              std::unique_ptr<AttachmentMap> attachments)>
-      GetOrDownloadCallback;
-
-  // An interface that embedder code implements to be notified about different
-  // events that originate from AttachmentService.
-  // This interface will be called from the same thread AttachmentService was
-  // created and called.
-  class Delegate {
-   public:
-    virtual ~Delegate() {}
-
-    // Attachment is uploaded to server and attachment_id is updated with server
-    // url.
-    virtual void OnAttachmentUploaded(const AttachmentId& attachment_id) = 0;
-  };
-
-  AttachmentService();
-  virtual ~AttachmentService();
-
-  // See SyncData::GetOrDownloadAttachments.
-  virtual void GetOrDownloadAttachments(
-      const AttachmentIdList& attachment_ids,
-      const GetOrDownloadCallback& callback) = 0;
-
-  // Schedules the attachments identified by |attachment_ids| to be uploaded to
-  // the server.
-  //
-  // Assumes the attachments are already in the attachment store.
-  //
-  // A request to upload attachments is persistent in that uploads will be
-  // automatically retried if transient errors occur.
-  //
-  // A request to upload attachments does not persist across restarts of Chrome.
-  //
-  // Invokes OnAttachmentUploaded on the Delegate (if provided).
-  virtual void UploadAttachments(const AttachmentIdList& attachment_ids) = 0;
-};
-
-}  // namespace syncer
-
-#endif  // COMPONENTS_SYNC_CORE_ATTACHMENTS_ATTACHMENT_SERVICE_H_