[csswg-drafts] [css-images] drop image-orientation angle values

heycam has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-images] drop image-orientation angle values ==
https://drafts.csswg.org/css-images/#the-image-orientation

The spec mentions in an issue that the angle values for `image-orientation` will probably be dropped. In [bug 1473450](https://bugzilla.mozilla.org/show_bug.cgi?id=1473450) I just removed Firefox's support for the angle values, and I don't think there were any other implementations. So it may be a good time to remove them now.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/2900 using your GitHub account