del element is not shown as deleted

[CYBAI]

While checking the html5accessibility testing page, I found we didn't show <del> element correctly.

Firefox:

Servo:

Also, this makes me notice that looks like we pass the del element test case bogusly 🤔 cc @emilio

Note: Built based on latest master on macOS 10.14.5

[CYBAI]

The simplest test case is

<del>test deleted</del>

[CYBAI]

Also, this makes me notice that looks like we pass the del element test case bogusly 🤔

Hmm, maybe I shouldn't say it's bogus because we do have the css attribute in

servo/resources/user-agent.css

Line 112 in 005320c

del, s, strike { text-decoration: line-through; }

But maybe we can test it better with a reftest? 🤔

[CYBAI]

Maybe this is related to #17887 👀?