[Sync] Move attachments code out of core/.

components/sync/engine/attachments/attachment_downloader.cc

Index: components/sync/engine/attachments/attachment_downloader.cc
diff --git a/components/sync/core_impl/attachments/attachment_downloader.cc b/components/sync/engine/attachments/attachment_downloader.cc
similarity index 61%
copy from components/sync/core_impl/attachments/attachment_downloader.cc
copy to components/sync/engine/attachments/attachment_downloader.cc
index 9483fbf26c14756e17dd55a90bb444bd50609321..7612e3c7784c90478d9619652d3226b5b160af9e 100644
--- a/components/sync/core_impl/attachments/attachment_downloader.cc
+++ b/components/sync/engine/attachments/attachment_downloader.cc
@@ -2,17 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "components/sync/core/attachments/attachment_downloader.h"
+#include "components/sync/engine/attachments/attachment_downloader.h"
 
-#include "components/sync/core/attachments/attachment_downloader_impl.h"
+#include "base/memory/ptr_util.h"
+#include "components/sync/engine_impl/attachments/attachment_downloader_impl.h"
 
 namespace syncer {
 
 AttachmentDownloader::~AttachmentDownloader() {}
 
-// Factory function for creating AttachmentDownloaderImpl.
-// It is introduced to avoid SYNC_EXPORT-ing AttachmentDownloaderImpl since it
-// inherits from OAuth2TokenService::Consumer which is not exported.
 std::unique_ptr<AttachmentDownloader> AttachmentDownloader::Create(
     const GURL& sync_service_url,
     const scoped_refptr<net::URLRequestContextGetter>&
@@ -23,9 +21,9 @@ std::unique_ptr<AttachmentDownloader> AttachmentDownloader::Create(
         token_service_provider,
     const std::string& store_birthday,
     ModelType model_type) {
-  return std::unique_ptr<AttachmentDownloader>(new AttachmentDownloaderImpl(
+  return base::MakeUnique<AttachmentDownloaderImpl>(
       sync_service_url, url_request_context_getter, account_id, scopes,
-      token_service_provider, store_birthday, model_type));
+      token_service_provider, store_birthday, model_type);
 }
 
 }  // namespace syncer