Update sync API to support attachments.

sync/api/attachments/attachment_service.h

Index: sync/api/attachments/attachment_service.h
diff --git a/sync/api/attachments/attachment_service.h b/sync/api/attachments/attachment_service.h
new file mode 100644
index 0000000000000000000000000000000000000000..d148b0c6a612dc62295a531226aaf6a81fb1b43e
--- /dev/null
+++ b/sync/api/attachments/attachment_service.h
@@ -0,0 +1,75 @@
+// 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_API_ATTACHMENTS_ATTACHMENT_SERVICE_H_
+#define SYNC_API_ATTACHMENTS_ATTACHMENT_SERVICE_H_
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "sync/api/attachments/attachment.h"
+#include "sync/base/sync_export.h"
+
+namespace syncer {
+
+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.
+class SYNC_EXPORT AttachmentService {
+ public:
+  // The result of a GetOrDownloadAttachments operation.
+  enum GetOrDownloadResult {
+    GET_SUCCESS,            // No error.
+    GET_NOT_FOUND,          // Attachment was not found or does not exist.
+    GET_UNSPECIFIED_ERROR,  // An unspecified error occurred.
+  };
+
+  typedef base::Callback<
+      void(const GetOrDownloadResult&, const AttachmentMap& attachments)>
+      GetOrDownloadCallback;
+
+  // The result of a DropAttachments operation.
+  enum DropResult {
+    DROP_SUCCESS,            // No error.
+    DROP_UNSPECIFIED_ERROR,  // An unspecified error occurred.
+  };
+
+  typedef base::Callback<void(const DropResult&)> DropCallback;
+
+  AttachmentService();
+  virtual ~AttachmentService();
+
+  // See SyncData::GetOrDownloadAttachments.
+  virtual void GetOrDownloadAttachments(
+      const AttachmentIdList& attachment_ids,
+      const GetOrDownloadCallback& callback) = 0;
+
+  // See SyncData::DropAttachments.
+  virtual void DropAttachments(const AttachmentIdList& attachment_ids,
+                               const DropCallback& callback) = 0;
+
+  // This method should be called when a SyncData is about to be added to the
+  // sync database so we have a chance to persist the Attachment locally and
+  // schedule it for upload to the sync server.
+  virtual void OnSyncDataAdd(const SyncData& sync_data) = 0;
+
+  // This method should be called when a SyncData is about to be deleted from
+  // the sync database so we can remove any unreferenced attachments from local
+  // storage.
+  virtual void OnSyncDataDelete(const SyncData& sync_data) = 0;
+
+  // This method should be called when a SyncData is about to be updated so we
+  // can remove unreferenced attachments from local storage and ensure new
+  // attachments are persisted and uploaded to the sync server.
+  virtual void OnSyncDataUpdate(const AttachmentIdList& old_attachment_ids,
+                                const SyncData& updated_sync_data) = 0;
+};
+
+}  // namespace syncer
+
+#endif  // SYNC_API_ATTACHMENTS_ATTACHMENT_SERVICE_H_