[Sync] Refactor AttachmentStore classes. Introduce concept of referrer.

sync/internal_api/public/attachments/attachment_service_impl.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 SYNC_INTERNAL_API_PUBLIC_ATTACHMENTS_ATTACHMENT_SERVICE_IMPL_H_
 #define SYNC_INTERNAL_API_PUBLIC_ATTACHMENTS_ATTACHMENT_SERVICE_IMPL_H_
 
 #include <deque>
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/threading/non_thread_safe.h"
 #include "net/base/network_change_notifier.h"
 #include "sync/api/attachments/attachment_store.h"
 #include "sync/internal_api/public/attachments/attachment_downloader.h"
 #include "sync/internal_api/public/attachments/attachment_service.h"
 #include "sync/internal_api/public/attachments/attachment_service_proxy.h"
 #include "sync/internal_api/public/attachments/attachment_uploader.h"
 #include "sync/internal_api/public/attachments/task_queue.h"
 
 namespace syncer {
 
 // Implementation of AttachmentService.
 class SYNC_EXPORT AttachmentServiceImpl
     : public AttachmentService,
       public net::NetworkChangeNotifier::NetworkChangeObserver,
       public base::NonThreadSafe {
  public:
+  // |attachment_store| is required. UploadAttachments reads attachment data
+  // from it. Downloaded attachments will be written into it.
+  //
   // |attachment_uploader| is optional. If null, attachments will never be
   // uploaded to the sync server and |delegate|'s OnAttachmentUploaded will
   // never be invoked.
   //
   // |attachment_downloader| is optional. If null, attachments will never be
   // downloaded. Only attachments in |attachment_store| will be returned from
   // GetOrDownloadAttachments.
   //
   // |delegate| is optional delegate for AttachmentService to notify about
   // asynchronous events (AttachmentUploaded). Pass NULL if delegate is not
   // provided. AttachmentService doesn't take ownership of delegate, the pointer
   // must be valid throughout AttachmentService lifetime.
   //
   // |initial_backoff_delay| the initial delay between upload attempts.  This
   // class automatically retries failed uploads.  After the first failure, it
   // will wait this amount of time until it tries again.  After each failure,
   // the delay is doubled until the |max_backoff_delay| is reached.  A
   // successful upload clears the delay.
   //
   // |max_backoff_delay| the maxmium delay between upload attempts when backed
   // off.
-  AttachmentServiceImpl(scoped_refptr<AttachmentStore> attachment_store,
+  AttachmentServiceImpl(scoped_ptr<AttachmentStore> attachment_store,
                         scoped_ptr<AttachmentUploader> attachment_uploader,
                         scoped_ptr<AttachmentDownloader> attachment_downloader,
                         Delegate* delegate,
                         const base::TimeDelta& initial_backoff_delay,
                         const base::TimeDelta& max_backoff_delay);
   ~AttachmentServiceImpl() override;
 
   // Create an AttachmentServiceImpl suitable for use in tests.
   static scoped_ptr<syncer::AttachmentService> CreateForTest();
 
   // AttachmentService implementation.
-  AttachmentStore* GetStore() override;
   void GetOrDownloadAttachments(const AttachmentIdList& attachment_ids,
                                 const GetOrDownloadCallback& callback) override;
   void UploadAttachments(const AttachmentIdSet& attachment_ids) override;
 
   // NetworkChangeObserver implementation.
   void OnNetworkChanged(
       net::NetworkChangeNotifier::ConnectionType type) override;
 
   // Use |timer| in the underlying TaskQueue.
   //
@@ skipping 15 matching lines @@
   void DownloadDone(const scoped_refptr<GetOrDownloadState>& state,
                     const AttachmentId& attachment_id,
                     const AttachmentDownloader::DownloadResult& result,
                     scoped_ptr<Attachment> attachment);
   void BeginUpload(const AttachmentId& attachment_id);
   void ReadDoneNowUpload(
       const AttachmentStore::Result& result,
       scoped_ptr<AttachmentMap> attachments,
       scoped_ptr<AttachmentIdList> unavailable_attachment_ids);
 
-  scoped_refptr<AttachmentStore> attachment_store_;
+  scoped_ptr<AttachmentStore> attachment_store_;
 
   // May be null.
   const scoped_ptr<AttachmentUploader> attachment_uploader_;
 
   // May be null.
   const scoped_ptr<AttachmentDownloader> attachment_downloader_;
 
   // May be null.
   Delegate* delegate_;
 
   scoped_ptr<TaskQueue<AttachmentId> > upload_task_queue_;
 
   // Must be last data member.
   base::WeakPtrFactory<AttachmentServiceImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AttachmentServiceImpl);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_ATTACHMENTS_ATTACHMENT_SERVICE_IMPL_H_