Set the predecessorid when creating records for upload.

services/sync/modules/engines/bookmarks.js

@@ -541,14 +541,15 @@ BookmarksStore.prototype = {
     }
 
     record.id = guid;
-    record.parentid = this._getParentGUIDForItemId(placeId);
+    record.parentid = this._getParentGUIDForId(placeId);
+    record.predecessorid = this._getPredecessorGUIDForId(placeId);
     record.encryption = cryptoMetaURL;
 
     this.cache.put(guid, record);
     return record;
   },
 
-  _getParentGUIDForItemId: function BStore__getParentGUIDForItemId(itemId) {
+  _getParentGUIDForId: function BStore__getParentGUIDForId(itemId) {
     let parentid = this._bms.getFolderIdForItem(itemId);
     if (parentid == -1) {
       this._log.debug("Found orphan bookmark, reparenting to unfiled");
@@ -558,6 +559,17 @@ BookmarksStore.prototype = {
     return GUIDForId(parentid);
   },
 
+  _getPredecessorGUIDForId: function BStore__getPredecessorGUIDForId(itemId) {
+    // Figure out the predecessor, unless it's the first item
+    let itemPos = Svc.Bookmark.getItemIndex(itemId);
+    if (itemPos == 0)
+      return;
+
+    let parentId = Svc.Bookmark.getFolderIdForItem(itemId);
+    let predecessorId = Svc.Bookmark.getIdForItemAt(parentId, itemPos - 1);
+    return GUIDForId(predecessorId);
+  },
+
   _getChildren: function BStore_getChildren(guid, items) {
     let node = guid; // the recursion case
     if (typeof(node) == "string") // callers will give us the guid as the first arg

services/sync/modules/type_records/bookmark.js

@@ -93,7 +93,7 @@ PlacesItem.prototype = {
   },
 };
 
-Utils.deferGetSet(PlacesItem, "cleartext", "type");
+Utils.deferGetSet(PlacesItem, "cleartext", ["predecessorid", "type"]);
 
 function Bookmark(uri) {
   this._Bookmark_init(uri);