Dialog: Some screen readers don't navigate correctly on open/close

[kfranqueiro]

The catalog page can be used to reproduce these issues: https://material-components.github.io/material-components-web-catalog/#/component/dialog

In iOS, upon opening a dialog with a MDC List in it (simple / confirmation), the screen reader is still focused on the button that opened the dialog, even though focus is on the first list item.

In iOS and OS X Safari, upon closing a dialog, the screen reader doesn't return to the button that opened the dialog. This is especially surprising in the case of Safari, since keyboard focus returns to the correct element, but for some reason the screen reader decides to navigate somewhere else. Chrome appears to be fine.

I'm not sure whether this is something we can resolve or work around, but it's worth investigating.