cc liberato, we bisected this back to https://chromium-review.googlesource.com/c/chromium/src/+/617922

I'll see if I can fix.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b8c7f9060a58b7165f429a28cb11da3ef26682d1

commit b8c7f9060a58b7165f429a28cb11da3ef26682d1
Author: Michael Thiessen <mthiesse@chromium.org>
Date: Wed Sep 06 20:29:15 2017

VR: Allow Control bars to hide before pausing VSync.

We've run into a host of issues where compositor updates are required to
get the controls into the correct state, so that restoring them doesn't
fail. This CL delays pausing VSync until the controls have been properly
hidden when entering VR.

Bug:  760970 
Change-Id: I9a80709e58d0588d456d8cbb1e6d9ede84ff6a3f
Reviewed-on: https://chromium-review.googlesource.com/645828
Reviewed-by: Biao She <bshe@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#500067}
[modify] https://crrev.com/b8c7f9060a58b7165f429a28cb11da3ef26682d1/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellImpl.java
[modify] https://crrev.com/b8c7f9060a58b7165f429a28cb11da3ef26682d1/chrome/android/javatests/src/org/chromium/chrome/browser/vr_shell/WebVrTransitionTest.java

Your change meets the bar and is auto-approved for M62. Please go ahead and merge the CL to branch 3202 manually. Please contact milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), bhthompson@(ChromeOS), abdulsyed@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

This issue has been approved for a merge. Please merge the fix to any appropriate branches as soon as possible!

If all merges have been completed, please remove any remaining Merge-Approved labels from this issue.

Thanks for your time! To disable nags, add the Disable-Nags label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/19ce8986420bda7ddf6b8874d65eee8924147019

commit 19ce8986420bda7ddf6b8874d65eee8924147019
Author: Michael Thiessen <mthiesse@chromium.org>
Date: Tue Sep 12 19:17:56 2017

VR: Allow Control bars to hide before pausing VSync.

We've run into a host of issues where compositor updates are required to
get the controls into the correct state, so that restoring them doesn't
fail. This CL delays pausing VSync until the controls have been properly
hidden when entering VR.

Bug:  760970 
Change-Id: I9a80709e58d0588d456d8cbb1e6d9ede84ff6a3f
Reviewed-on: https://chromium-review.googlesource.com/645828
Reviewed-by: Biao She <bshe@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#500067}(cherry picked from commit b8c7f9060a58b7165f429a28cb11da3ef26682d1)
Reviewed-on: https://chromium-review.googlesource.com/663279
Reviewed-by: Christopher Grant <cjgrant@chromium.org>
Cr-Commit-Position: refs/branch-heads/3202@{#178}
Cr-Branched-From: fa6a5d87adff761bc16afc5498c3f5944c1daa68-refs/heads/master@{#499098}
[modify] https://crrev.com/19ce8986420bda7ddf6b8874d65eee8924147019/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellImpl.java
[modify] https://crrev.com/19ce8986420bda7ddf6b8874d65eee8924147019/chrome/android/javatests/src/org/chromium/chrome/browser/vr_shell/WebVrTransitionTest.java

Entered and exited WebVR multiple times on Pixel XL 62.0.3202.38 and could not repro. Marking as verified.