When dragging a group of table rows (e.g. in a hierarchical menu), the classes for "tree-child", "tree-child-first", and "tree-child-horizontal" are not added. This makes it so that the visual representation of the tree being dragged is not shown. The last class, "tree-child-last" actually continues to work.
Here's a screenshot *while dragging* an item. You can see the lack of tree indicators except for the last item (Views).
Fix the addition of classes in Drupal.tableDrag.prototype.row.prototype.findChildren().
Review and test.
User interface changes
None, other than fixing the functionality