[Sync] Add size and crc32c to AttachmentId.

sync/internal_api/public/base/attachment_id_proto.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_BASE_ATTACHMENT_ID_PROTO_H_
 #define SYNC_INTERNAL_API_PUBLIC_BASE_ATTACHMENT_ID_PROTO_H_
 
+#include "base/basictypes.h"
 #include "sync/base/sync_export.h"
 #include "sync/protocol/sync.pb.h"
 
 namespace syncer {
 
 // Helper functions that are logically part of sync_pb::AttachmentIdProto.
 
 // Creates a unique AttachmentIdProto.
-SYNC_EXPORT_PRIVATE sync_pb::AttachmentIdProto CreateAttachmentIdProto();
+//
+// |size| is the size in bytes of the attachment identified by this proto.
+//
+// |crc32c| is the crc32c of the attachment identified by this proto.
+SYNC_EXPORT_PRIVATE sync_pb::AttachmentIdProto CreateAttachmentIdProto(
+    size_t size,
+    uint32_t crc32c);
 
 // Creates an AttachmentMetadata object from a repeated field of
 // AttachmentIdProto objects.
 //
 // Note: each record in the AttachmentMetadata will be marked as "on the
 // server".
 SYNC_EXPORT_PRIVATE sync_pb::AttachmentMetadata CreateAttachmentMetadata(
     const google::protobuf::RepeatedPtrField<sync_pb::AttachmentIdProto>& ids);
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_BASE_ATTACHMENT_ID_PROTO_H_