I don't see any errors about failing to play video - I don't think this is a dupe of 761587.

Both when clicking the "enter VR" button, or when I put the phone in a headset I end up in VR shell.

The main issue I'm seeing is the timeout if frames aren't submitted within 5 seconds after starting presentation.  When I let the device sit for ~30 seconds, I eventually see the experience start.

Note I was testing with a private build that also removed gesture requirements from video playback - so the workaround to use displayActivate's user gesture as proposed in 761587 may also be necessary here.

The permanent black screen issue as described in the title and initial description no longer repros as of Chrome 64.0.3274.0. So closing this issue.

Note that the description in #4 is the same as bug 763000 which is still open.