[csswg-drafts] [css-align] Serialization of the alignment properties.

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

== [css-align] Serialization of the alignment properties. ==
Should properties serialize the default values? Right now Blink and WebKit do so, which I think it's a bug.

In particular:

```css
align-items: unsafe start;
```

Serializes in Blink as `unsafe start`, and only `start` in FF. I think the computed value should serialize to the shortest form possible.

This is annoying because it causes a lot of WPT failures on Gecko.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/2229 using your GitHub account