[css-ui] Inheritance and initial value

[ewilligers]

Test that CSS Basic User Interface properties inherit.
Test that initial values match the spec.
https://drafts.csswg.org/css-ui/#property-index

[ewilligers]

Edge gives 'invert' as the initial computed value for outline-color (consistent with spec) but Chrome/Firefox/Safari give rgb(...).

Edge does not support caret-color. No browser gives 'auto' as the initial computed value for caret-color (consistent with spec); Chrome/Firefox/Safari give rgb(...).

Only Chrome supports user-select.

[foolip]

The failing Travis build in this PR was due to #13112, which has now been resolved. To recover, rebase the PR on master and push. (Simply restarting the Travis jobs may also work, not tested.)

[svgeesus]

LGTM

[ewilligers]

@svgeesus can you please merge this. GitHub tells me "Review required".

[foolip]

Glossy review LGTM

[frivoal]

Hmmm. Sorry for the slow review. I think we should actually revert / fix this:

• For color properties, getComputedStyle returns the used value, not the computed value. They are different, but your asserts are written assuming the computed value. Hence why you get rgb(…) when you were expecting auto.
• For the invert color of the outline-color property, you should check if the invert keyword is supported at all. If it is, it should be the initial value, but if it is not, having currentColor be the initial value is spec compliant, and should not cause the test to fail.

[frivoal]

Just noticed you had filed a follow up in #13748 will continue discussing there.