sync: Enable typed tombstones commits

sync/engine/commit_util.cc

Index: sync/engine/commit_util.cc
diff --git a/sync/engine/commit_util.cc b/sync/engine/commit_util.cc
index 45bc2bbf1e219f71fb5ea4b4ce5f07486fed9357..36b7c06b9c8c0dd9557ff53b57ac4910960a1532 100644
--- a/sync/engine/commit_util.cc
+++ b/sync/engine/commit_util.cc
@@ -182,6 +182,10 @@ void BuildCommitItem(
   // Deletion is final on the server, let's move things and then delete them.
   if (meta_entry.GetIsDel()) {
     sync_entry->set_deleted(true);
+
+    sync_pb::EntitySpecifics type_only_specifics;
+    AddDefaultFieldValue(meta_entry.GetModelType(),
+                         sync_entry->mutable_specifics());
   } else {
     SetEntrySpecifics(meta_entry, sync_entry);
   }