The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f9c23f65984eaaac896b56d17ac0fe1fe621bca7

commit f9c23f65984eaaac896b56d17ac0fe1fe621bca7
Author: Michael Thiessen <mthiesse@chromium.org>
Date: Fri Jul 14 16:27:52 2017

VR: Don't attempt to cancel VR entry if we're already in VR.

Headset NFC scan can pause and resume (without stopping) us while
we're already in VR, so we stay in VR while this is happening.
However, when we get paused we want to cancel VR entry so we don't
enter VR while paused. This CL just adds a check to see if we're in
VR before attempting to cancel entry.

Bug:  742509 
Change-Id: Ib0cdac3c7e10e5206410835f949f318c73e9349f
Reviewed-on: https://chromium-review.googlesource.com/570742
Reviewed-by: Yash Malik <ymalik@chromium.org>
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486769}
[modify] https://crrev.com/f9c23f65984eaaac896b56d17ac0fe1fe621bca7/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java