The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/01981ce017b86749e7fbaac6722b66af15242acc

commit 01981ce017b86749e7fbaac6722b66af15242acc
Author: Ian Vollick <vollick@chromium.org>
Date: Thu Jun 21 04:59:00 2018

[vr] When recentering, only reset yaw

With this change, recentering the UI will preserve the content scale as
well as its pitch, but it's yaw will be reset to zero. I.e., it will be
positioned in front of you, but it will be the same size and will be
in the same spot with respect to the horizon.

Bug:  854860 
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:linux_vr;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: Ifced628481bdfbbae473bb530df6f766f5728485
Reviewed-on: https://chromium-review.googlesource.com/1109393
Commit-Queue: Ian Vollick <vollick@chromium.org>
Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569160}
[modify] https://crrev.com/01981ce017b86749e7fbaac6722b66af15242acc/chrome/browser/vr/elements/repositioner.cc
[modify] https://crrev.com/01981ce017b86749e7fbaac6722b66af15242acc/chrome/browser/vr/elements/repositioner.h
[modify] https://crrev.com/01981ce017b86749e7fbaac6722b66af15242acc/chrome/browser/vr/testapp/vr_test_context.cc
[modify] https://crrev.com/01981ce017b86749e7fbaac6722b66af15242acc/chrome/browser/vr/testapp/vr_test_context.h
[modify] https://crrev.com/01981ce017b86749e7fbaac6722b66af15242acc/chrome/browser/vr/ui_scene_creator.cc
[modify] https://crrev.com/01981ce017b86749e7fbaac6722b66af15242acc/chrome/browser/vr/ui_unittest.cc

This bug requires manual review: M68 has already been promoted to the beta branch, so this requires manual review
Please contact the milestone owner if you have questions.
Owners: cmasso@(Android), kariahda@(iOS), bhthompson@(ChromeOS), abdulsyed@(Desktop)

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

Is this a regression in M68? Can you verify the fix in canary.

I have verified the behavior in Canary, yes. It is a regression in M68 due to a misunderstanding of the UX spec.

Here's a bit more context. In this change (https://chromium-review.googlesource.com/c/chromium/src/+/1104818), I'd merged back a change to M68 to avoid repositioning when we recenter in VR, per the UX review.

However, that was a misunderstanding of the review feedback. What was needed was not avoiding repositioning entirely, just resetting the yaw. This change corrects the behavior that was merged back. And as mentioned in the previous comment, I have verified this fix in Canary.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/af4377584f3cf0390368908685caa47de47b86a2

commit af4377584f3cf0390368908685caa47de47b86a2
Author: Ian Vollick <vollick@chromium.org>
Date: Mon Jun 25 23:10:56 2018

[vr] When recentering, only reset yaw

With this change, recentering the UI will preserve the content scale as
well as its pitch, but it's yaw will be reset to zero. I.e., it will be
positioned in front of you, but it will be the same size and will be
in the same spot with respect to the horizon.

Bug:  854860 
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:linux_vr;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: Ifced628481bdfbbae473bb530df6f766f5728485
Reviewed-on: https://chromium-review.googlesource.com/1109393
Commit-Queue: Ian Vollick <vollick@chromium.org>
Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#569160}(cherry picked from commit 01981ce017b86749e7fbaac6722b66af15242acc)
Reviewed-on: https://chromium-review.googlesource.com/1113845
Reviewed-by: Ian Vollick <vollick@chromium.org>
Cr-Commit-Position: refs/branch-heads/3440@{#520}
Cr-Branched-From: 010ddcfda246975d194964ccf20038ebbdec6084-refs/heads/master@{#561733}
[modify] https://crrev.com/af4377584f3cf0390368908685caa47de47b86a2/chrome/browser/vr/elements/repositioner.cc
[modify] https://crrev.com/af4377584f3cf0390368908685caa47de47b86a2/chrome/browser/vr/elements/repositioner.h
[modify] https://crrev.com/af4377584f3cf0390368908685caa47de47b86a2/chrome/browser/vr/testapp/vr_test_context.cc
[modify] https://crrev.com/af4377584f3cf0390368908685caa47de47b86a2/chrome/browser/vr/testapp/vr_test_context.h
[modify] https://crrev.com/af4377584f3cf0390368908685caa47de47b86a2/chrome/browser/vr/ui_scene_creator.cc
[modify] https://crrev.com/af4377584f3cf0390368908685caa47de47b86a2/chrome/browser/vr/ui_unittest.cc

Verified in Chrome Beta 68.0.3440.40