Update sync API to support attachments.

sync/api/attachments/attachment_service_base.cc

Index: sync/api/attachments/attachment_service_base.cc
diff --git a/sync/engine/update_handler.cc b/sync/api/attachments/attachment_service_base.cc
similarity index 57%
copy from sync/engine/update_handler.cc
copy to sync/api/attachments/attachment_service_base.cc
index 308fee95bb1074c197b6973f38b49eb017d9ba7c..b977b4310601095aff1353855245e1aa4bd29c89 100644
--- a/sync/engine/update_handler.cc
+++ b/sync/api/attachments/attachment_service_base.cc
@@ -2,13 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "sync/engine/update_handler.h"
+#include "sync/api/attachments/attachment_service_base.h"
 
 namespace syncer {
 
-UpdateHandler::UpdateHandler() {}
-
-UpdateHandler::~UpdateHandler() {}
+AttachmentServiceBase::AttachmentServiceBase() {}
 
+AttachmentServiceBase::~AttachmentServiceBase() {}
 
 }  // namespace syncer