components: Cleanup class/struct fwd declarations

components/sync/model/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_MODEL_ATTACHMENTS_ATTACHMENT_SERVICE_H_
 #define COMPONENTS_SYNC_MODEL_ATTACHMENTS_ATTACHMENT_SERVICE_H_
 
 #include <memory>
 
 #include "base/callback.h"
 #include "base/memory/weak_ptr.h"
 #include "components/sync/model/attachments/attachment.h"
 
 namespace syncer {
 
 class AttachmentDownloader;
-class AttachmentStore;
 class AttachmentStoreForSync;
 class AttachmentUploader;
 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
@@ skipping 52 matching lines @@
   //
   // 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_MODEL_ATTACHMENTS_ATTACHMENT_SERVICE_H_