bug#51883: 29.0.50; Command to get accidentally deleted frames back

[Juri Linkov]

>>> IIUC framesets are designed to be serializable so they shouldn't hold on
>>> to external data like buffers and windows, so such 16 elements should
>>> cost very little in terms of heap use.
>> OTOH, since framesets are designed to be serializable, isn't it
>> overkill to use framesets in the same session?
>
> Not sure what you mean by "overkill".  AFAIK it makes them more lightweight.

Without framesets it doesn't require loading frameset.el.

>> For example, `clone-frame` doesn't use framesets, and the effect of
>> `clone-frame` should be the same as what `undelete-frame` does.
>
> Except it actually creates a frame, so it requires a lot more resources.

I don't understand: `clone-frame` creates a new frame with `make-frame`,
and `undelete-frame` creates a new frame with `make-frame-on-display`.