* fix: errors of replaying iframe records
error1:
HierarchyRequestError: Failed to execute 'appendChild' on 'Node': Nodes of type '#document' may not be inserted inside nodes of type '#document-fragment'.
code: parent.appendChild(target)
error2:
Uncaught DOMException: Failed to execute 'appendChild' on 'Node': Only one element on document allowed.
code: parent.appendChild(target);
* improve the comment for bugfix
016a5020fc