Incorporate host-language unique computedrole string for reserved native elements with no direct ARIA equivalent

[cookiecrook]

Incorporate Example 3 in https://w3c.github.io/core-aam/#roleMappingComputedRole

When host language elements do not have an exact or equivalent mapping to a valid, non-abstract role, the related Accessibilty API Mapping extension specification MAY specify a unique computedrole string as the return value for interoperability testing purposes, such as <video> -> "html-video" in [HTML-AAM]. However, authors MUST NOT use any host-language-prefixed computedrole string in the role attribute (such as html-video), unless the token also matches valid, defined role (such as dpub-chapter). User Agents MUST ignore any abstract or invalid role token.

EXAMPLE 3

<video> <!-- computedrole returns "html-video" -->
<main role="html-video"> <!-- Author error. computedrole returns "main" -->

[cookiecrook]

I thought this one existed already, but I could not find it in HTML-AAM. I was probably thinking of a related tracker in the main ARIA spec repo.

[cookiecrook]

Some related discussion in the following:

• Role parity: consider "native-" or "host-" role prefix for host language elements (including audio/video, but not limited to media) where custom ARIA implementations cannot (yet) match the native implementation's accessibility. aria#529
• Need a decision on what the computedrole should return on extension specs aria#1887

Related spec commit:

• w3c/core-aam@5d6012b

[scottaohara]

Looks like the computed role content got deleted when HTML AAM was converted form the details/summary/table layout to just tables.

I'll get these all back into the spec with the PR to address this.

[spectranaut]

Ugh, sorry @scottaohara, I guess that was my fault :(

[scottaohara]

No more your fault than mine, since I didn’t catch it