Update ATK mappings for ins and del

[joanmarie]

• Update the platform role mappings to ATK_ROLE_CONTENT_INSERTION and
  ATK_ROLE_CONTENT_DELETION respectively. These new roles have landed
  in both ATK and AT-SPI2.
• Add 'xml-roles' AtkObject attribute on each because if user agents use
  the old role (ATK_ROLE_SECTION), ATs will need a fallback to find out
  what the elements' role should be.

Closes #218

The following tasks have been completed:

• Confirmed there are no ReSpec/BikeShed errors or warnings.
• Modified Web platform tests (link to pull request)

Implementation commitment:

• WebKit (https://bugs.webkit.org/show_bug.cgi?id=)
• Chromium (https://bugs.chromium.org/p/chromium/issues/detail?id=)
• Gecko (https://bugzilla.mozilla.org/show_bug.cgi?id=)

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Preview | Diff

[joanmarie]

Regarding implementation commitment, I'll try to do the implementations soon. :) I'll have to do them for the new ARIA roles anyway, so might as well do it at the same time....

[marcoscaceres]

@joanmarie, thanks great to hear. I should update the template to include Orca, instead of just the browser engines? Be great to track progress/implantation commitments from you.

@joanmarie, also, our IPR bot is complaining that you are not a member of the WebApps WG. It would be great if you could join as an implementer. Anything I or @LJWatson can do to help with that?

[joanmarie]

@marcoscaceres I used to be a member of WebPlatform. I guess I need to add myself to WebApps. Regarding Orca and "implementation":

1. As I trust you know, Orca is a screen reader; not a user agent. I think we/you want implementations in user agents.
2. When I say "implementations" I meant I would implement them in WebKitGtk, Chromium/Blink, and possibly Gecko; not in Orca. (I'll add support in Orca too, of course, but see item 1.)

[joanmarie]

@marcoscaceres I should now be a WebApps member.

[marcoscaceres]

I’m still learning so I honestly don’t know how this gets implemented 👶 I’m keen to learn tho, as I can at least help with reviews or even implement on the Gecko side.

So it sounds like the current template is for implementation commitment is fine. We should add file the appropriate bugs on each browser vendor so this doesn’t get lost.

If we can also get some Web Platform Tests, that would be amazing.

[marcoscaceres]

All green regarding IPR commitment! Thanks for joining the WG. Looking forward to collaborating and learning from you.

[joanmarie]

WebKit is done: https://trac.webkit.org/changeset/247349. Note that I did it as part of a bigger, ARIA patch.