At ToT on October 2, I can repro this, but (within your first set of steps), at (5), the browser crashed for me, rather than returning to the webpage.  I immediately restart it, return to the 03-vr-presentation page, and then cannot Enter VR via the button.

Copying Michael as he's most aware of DON flow details/issues.

I've made this P1, but based on the fact that the issue shows only if the 'X'/'Gear' is touched, this could be dropped to P2 if this isn't exposing a critical underlying problem.

Michael, can you please take a look?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/158378368460f4fd0a70f2ddc34ea4683b22d217

commit 158378368460f4fd0a70f2ddc34ea4683b22d217
Author: Michael Thiessen <mthiesse@chromium.org>
Date: Wed Oct 11 20:42:37 2017

VR: Fix DON flow permanently failing after backing out of DON flow

I missed updating the state saying we were actually in the DON flow
when I added the s8 workaround ;)

Bug:  770245 
Change-Id: I858ae1c5daecf7b45c9206ed6477f29939729a58
Reviewed-on: https://chromium-review.googlesource.com/713748
Reviewed-by: Yash Malik <ymalik@chromium.org>
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#508100}
[modify] https://crrev.com/158378368460f4fd0a70f2ddc34ea4683b22d217/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
[modify] https://crrev.com/158378368460f4fd0a70f2ddc34ea4683b22d217/device/vr/android/gvr/gvr_device.cc

Issue is still reproducible in chrome Dev 64.0.3249.0

reproduction steps:
1. Open https://webvr.info/samples/03-vr-presentation.html
2. Hit "Enter VR" button
3. Don't put device in the headset when asked to. Before syncing the controller, hit the x in the upper left hand corner to exit the DON flow.
=> User is returned to Android Home screen, Chrome is running in the background at this point.
4. Open Chrome again
=> Error message is displayed on top of the page. New error message pops up every time when "Enter VR" button is clicked.

vsupruniuk, I think you're running into: https://bugs.chromium.org/p/chromium/issues/detail?id=759575

This is a known (separate) issue. Can you please confirm that the failure in that case isn't permanent, and only lasts ~10 seconds?

Please mark this issue as fixed/verified if that's the case.

Right, it's possible to enter VR again after ~10 sec. Closing the issue.