Investigate "0 items selected" message in VoiceOver for MdSelect

[kara]

Currently in VoiceOver, the select will always read "0 items selected", even if aria-selected, aria-owns, aria-posinset, and aria-setsize are set. It appears to be this way in Material 1 as well. Needs investigation / fixing.

[HumanMedia]

+1
We really need this fixed as well. Trying to do a site for a major organization for disabled. This is a big problem for us.

[naomiblack]

We think this is also related to an issue we're seeing in aXe testing for md-select with child options.

[naomiblack]

possibly connected to #6382

[devversion]

This issue seems to be more related to the general accessibility approach of the select. Since the select options are displayed dynamically outside of the <mat-select> element, the options won't be found by screenreaders if the panel is closed.

This means that the aria-selected option can't be found, and there will be always 0 items selected.

I think that it would be better to keep the list options permanently in the DOM, and also inside of the <mat-select> element.

On VoiceOver (even with aria-owns) the active option doesn't seem to be announced either (when using the arrow keys). Meaning that the select isn't really usable with VoiceOver.