Chrome Version       : 69.0.3497.100
OS Version: 
URLs (if applicable) : https://codebin.googleplex.com/view/ghechdnvwfx
Other browsers tested:
  Add OK or FAIL after other browsers where you have tested this issue:
     Safari:
    Firefox:
    IE/Edge:

What steps will reproduce the problem?
1. When an element and the element referred to by its aria-describedby are both in a shadowRoot AND the element referred to by its aria-describedby is hidden (CSS display:none or visibility:hidden), when using linear nav to go to the element, the content of the element referred to by aria-describeby is not read. However, in all other combinations it is read-- that is, if the element referred to by aria-describedby is not hidden via CSS, as well as when elements are not in shadowRoot.

In the example, the SR reads "bar" for all lines (ignore lines that say bar) except the first.

What is the expected result?

Behavior in shadowRoot & outside of shadowRoot should be consistent.

Note: With VoiceOver (MacOS), aria-description is not read for any of the four lines.

Screencast: http://go/scrcast/NjU0Mzc2NjkzMjQyMjY1NnwzZmM4NTkzYS1iMA

UserAgentString: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36