OS: Chrome
Tested on Canary (61) but experienced in previous versions 




In the notification center, when I hover over a Chrome OS notification, the X close button appears to get rid of the notification. However, that only appears when using the mouse or using tab. You can't get there using ChromeVox navigation, Search + Right, which is really confusing. If you happened to know that you needed to use tab to get to the chrome os notification close button, then all your hear is "notification close button", and it's not associated to any of the notifications, so you don't know which one you are closing. 

These need to be navigable with ChromeVox navigation, and be associated with the actual notification.