Not sure if this is doable on ToT, but if something requests DOFF with an explanation and the user hits 'Exit VR' but then backs out of DOFF, they're returned to the request to DOFF. Clicking 'Exit VR' again leads to a assertion failure because the DOFF client was already responded to.
Comment 1 by mthiesse@chromium.org
, Feb 15 2018