Jetpack: Hidden textarea in comments needs aria-hidden="true"

[NicktheGeek]

During an accessibility audit for a site using Jetpack with the comments module it was reported that the comment form needed some changes.

This textarea has a lot of styles to hide it, but it's still in the DOM. Add aria-hidden="true" to remove this from the Accessibility API.

<textarea aria-hidden="true" tabindex="-1" style="position: absolute; top: -999px; left: 0px; right: auto; bottom: auto; border: 0px; padding: 0px; box-sizing: content-box; word-wrap: break-word; overflow: hidden; transition: none; height: 0px !important; min-height: 0px !important; font-family: Arial, Helvetica, Tahoma, Verdana, sans-serif; font-size: 14px; font-weight: 400; font-style: normal; letter-spacing: 0px; text-transform : none; text-decoration: none solid rgba(0, 0, 0, 0.7); word-spacing: 0px; text-indent: 0px; line-height: normal; width: 577px;" class="autosizejs ">

Steps to reproduce the issue

1. Enable Comments for WordPress and the Jetpack module
2. Visit a post or page with comments enabled
3. View page source/inspect the comment form

What I expected

<textarea> hidden with JS/CSS should also include aria-hidden="true" attribute.

What happened instead

The aria-hidden attribute is not present.

[uxcitizen]

Also tracking in VIP ticket: #88679

[uxcitizen]

Element is created in jquery.autoresize.js.

I've drafted a proposed revision in D23814-code.

[alexiskulash]

This revision has been deployed in r187941.

Thank you @NicktheGeek @uxcitizen @jeherve and @GaryJones!