Chrome Version: 57.0.2955.0
OS: Chrome

What steps will reproduce the problem?
(1) Enable chromevox
(2) Navigate to permission.site in url bar and press enter
(3) Navigate to the notification button to trigger a permission notification 

First, observe that there are multiple verbalizations from ChroemVox

Second, note that you can access the URL, close button, allow and block buttons, but not access what Chrome OS is actually seeking permission for. There is text there that says "show notifications", which is key text. However, ChromeVox can't access it.