aria-checked can be toggled when element is disabled (a11y issue)

[godinger]

Example: https://jsbin.com/cikijif/3/edit?html,output

Expected Behavior: I would not expect this property to be toggle-able when element is disabled.

Actual Behavior: This disabled paper-checkbox's aria-checked property can be changed when using Chromevox. Simply navigate to the checkbox with the appropriate ChromeVox modifier keys and press spacebar when on the checkbox. While it will not appear as checked, if you inspect the element you'll see aria-checked can be changed (it toggles between true and false).