code: function(original, clone) {
      if (goog.isNull(original)) {
        return;
      }
  
      var cloneFull = original.getChildCount() == clone.getChildCount();
      if (cloneFull) {
        var cloneIndex = copyParentStack.indexOf(clone);
        if (cloneIndex != -1) {
          copyParentStack.splice(cloneIndex, 1);
        }
      }
    }
docs: Removes a node from the parent stack, if that node has already reached its
  target number of children.
  @param {?lf.structs.TreeNode} original The original node.
  @param {!lf.structs.TreeNode} clone The corresponding cloned node.