Per css-ui-4, setting `appearance: none` is supposed to suppress the
creation of a native-looking widget for stuff like checkboxes, radio
buttons, etc.
This patch implements this behavior by simply falling back to creating
a layout node based on the CSS `display` property in such cases.
This fixes an issue on the hey.com imbox page where we were rendering
checkboxes on top of sender profile photos.
(cherry picked from commit 58c523ae46af90ab17d6b98966d97fa776ae2bf4)
