NSAccessibility has API (old and new) through which an AT can obtain the scrollbars associated with a scrollview. While ARIA lacks a "scrollview" role, the spec states:

Authors MUST set the aria-controls attribute on the scrollbar element to reference the scrollable area it controls.

If authors do that, then user agents could implement NSAccessibility's scroll-bar API exposing the scrollbars on the controlled element.

My question is: Should user agents do this implementation, or was it deliberately left out of the spec?

@cookiecrook: Your/Apple's input would be much appreciated. Thanks in advance!