turbo-frame with text only not rendering on restoration visits

[tpaulshippy]

Steps to reproduce

1. Make a frame with only text in it.
2. Use a turbo-action "advance" link to advance that frame to another URL.
3. Click Back in your browser.

Expected

The original text is restored.

Actual

The frame is blank.

@tleish explained this here:

I'm not sure the turbo-frame with text only not rendering on restoration visits is a bug. I believe turbo uses cloneNode to cache html. If the frame has no nodes to cache (text only), then it doesn't cache it.

Originally posted by @tleish in #1241 (comment)