--- a/services/sync/modules/stores.js
+++ b/services/sync/modules/stores.js
@@ -125,16 +125,28 @@ Store.prototype = {
   wrap: function Store_wrap() {
     throw "override wrap in a subclass";
   },
 
   wrapItem: function Store_wrapItem() {
     throw "override wrapItem in a subclass";
   },
 
+  wrapDepth: function BStore_wrapDepth(guid, items) {
+    if (typeof(items) == "undefined")
+      items = {};
+    for (let childguid in this._itemCache) {
+      if (this._itemCache[childguid].parentid == guid) {
+        items[childguid] = this._itemCache[childguid].depth;
+        this.wrapDepth(childguid, items);
+      }
+    }
+    return items;
+  },
+
   changeItemID: function Store_changeItemID(oldID, newID) {
     throw "override changeItemID in a subclass";
   },
 
   getAllIDs: function Store_getAllIDs() {
     throw "override getAllIDs in a subclass";
   },