Florian/pre wrap auto trim

[frivoal]

This adds text-space-collapse: preserve-auto and text-space-collapse: preserve-trim to css-text-4, and explains white-space: pre-wrap-auto in terms of the former.

Also includes a small bug fix.

[fantasai]

preserve-spaces-auto should refer explicitly to system conventions, since that's the whole point of it. It's not UA-defined. It's OS-defined.

(Also, preserve-trim should note that it's at-risk, and we're not sure if it's needed. We need use cases, and they should help clarify if both leading and trailing spaces should be trimmed.)

[frivoal]

preserve-spaces-auto should refer explicitly to system conventions, since that's the whole point of it. It's not UA-defined. It's OS-defined.

Not sure. IE's behavior and Safari's behavior are arguably following OS standards. But Chrome does the same cross platform. And we were not trying to force them to change. I think adding a "Should follow platform convensions" would be good, since indeed that's a large part of the intent, but I'd like to keep it as a should. Sounds OK?

preserve-trim should note that it's at-risk

Will do.

[frivoal]

@fantasai Is this better?