queuePush = function (node) {
            if (node.children && oldNodeMap[node.tagID]) {
                queue.push(node);
            }
        }
Adds elements to the queue for generateChildEdits.
Only elements (and not text nodes) are added. New nodes (ones that aren't in the
old nodeMap), are not added here because they will be added when generateChildEdits
creates the elementInsert edit.