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

components/sync_driver/generic_change_processor_factory.cc

Index: components/sync_driver/generic_change_processor_factory.cc
diff --git a/components/sync_driver/generic_change_processor_factory.cc b/components/sync_driver/generic_change_processor_factory.cc
index 1a7a8d9182a5ace023945f15af709df04b92e25c..ecc766a10d9a909c0362f094a03779162679f97e 100644
--- a/components/sync_driver/generic_change_processor_factory.cc
+++ b/components/sync_driver/generic_change_processor_factory.cc
@@ -24,13 +24,10 @@ GenericChangeProcessorFactory::CreateGenericChangeProcessor(
     SyncApiComponentFactory* sync_factory) {
   DCHECK(user_share);
   return make_scoped_ptr(new GenericChangeProcessor(
-                             type,
-                             error_handler,
-                             local_service,
-                             merge_result,
-                             user_share,
-                             sync_factory,
-                             local_service->GetAttachmentStore())).Pass();
+                             type, error_handler, local_service, merge_result,
+                             user_share, sync_factory,
+                             local_service->GetAttachmentStoreForSync()))
+      .Pass();
 }
 
 }  // namespace sync_driver