We've got tests that test accepting a requested DOFF flow in the case of startActivity being called in VR, but we don't have anything that ensures onDenied() is always called when the DOFF flow is rejected by the user.

There are a number of untested ways DOFF can be accepted or rejected, like:
- User rejects the in-VR exit prompt pre-DOFF.
- User backs out of the DOFF.
- User exits VR while seeing in-VR exit prompt.
- User leaves and comes back to Chrome while seeing DOFF.
- DOFF flow fails due to exception/error from SDK.