Backend tablet/mobile preview seems to beak CSS from the iFrame preview in 5.9.3

[covertnine]

Hey,

Just noticed this on the latest update. I think it was from a 5.9.2 or 5.9.3 update, but it could just be in the regular 5.9 update. Basically, if you use the backend mobile/tablet previews, they break the CSS completely. There's no CSS applied from the custom-editor-style.css or the client-editor.css files.

I'm poking around trying to see what changed, but it may just be a matter of making sure the CSS files get inserted to the mobile previews, somehow.... any help would be appreciated here. Could be a theme thing to fix..

See screenshot--this is with latest block plugin/theme.

-Tim

[covertnine]

Looks like it will take some code refactoring:
https://developer.wordpress.org/block-editor/how-to-guides/block-tutorial/applying-styles-with-stylesheets/

On the theme side I think I can handle the function updates to make sure the block editor CSS is pushing to the mobile previews, but would like some help on refactoring blocks if we need to stay compatible.

-Tim

[covertnine]

Looks like this is a bug other people are also dealing with so I'll just keep an eye on this one for now.

WordPress/gutenberg#38673
WordPress/gutenberg#39373