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

sync/api/fake_syncable_service.cc

Index: sync/api/fake_syncable_service.cc
diff --git a/sync/api/fake_syncable_service.cc b/sync/api/fake_syncable_service.cc
index d2177e9a0c1f0668e5160ab86e6dbae33acc0d99..ec7b90cf53be24bd54de84b09e4988d835d2f66b 100644
--- a/sync/api/fake_syncable_service.cc
+++ b/sync/api/fake_syncable_service.cc
@@ -26,8 +26,8 @@
 }
 
 void FakeSyncableService::set_attachment_store(
-    scoped_ptr<AttachmentStore> attachment_store) {
-  attachment_store_ = attachment_store.Pass();
+    const scoped_refptr<AttachmentStore>& attachment_store) {
+  attachment_store_ = attachment_store;
 }
 
 const AttachmentService* FakeSyncableService::attachment_service() const {
@@ -70,9 +70,8 @@
   return process_sync_changes_error_;
 }
 
-scoped_ptr<AttachmentStore> FakeSyncableService::GetAttachmentStoreForSync() {
-  return attachment_store_ ? attachment_store_->CreateAttachmentStoreForSync()
-                           : scoped_ptr<AttachmentStore>();
+scoped_refptr<AttachmentStore> FakeSyncableService::GetAttachmentStore() {
+  return attachment_store_;
 }
 
 void FakeSyncableService::SetAttachmentService(