The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d

commit 618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d
Author: Ian Vollick <vollick@chromium.org>
Date: Thu Feb 01 00:56:41 2018

[vr] Avoid snap at the onset of window repositioning

With this change, we begin repositioning based on laser direction deltas
once repositioning is enabled. Also adds a scrim to the content quad
while repositioning is happening. We also update controller labels.

Bug:  800563 , 800556 
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_vr;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I19bdc286c7b7be2dc5df8a6690b965098959559e
Reviewed-on: https://chromium-review.googlesource.com/894902
Commit-Queue: Ian Vollick <vollick@chromium.org>
Reviewed-by: Christopher Grant <cjgrant@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533498}
[modify] https://crrev.com/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d/chrome/app/generated_resources.grd
[modify] https://crrev.com/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d/chrome/browser/vr/elements/repositioner.cc
[modify] https://crrev.com/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d/chrome/browser/vr/elements/repositioner.h
[modify] https://crrev.com/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d/chrome/browser/vr/elements/repositioner_unittest.cc
[modify] https://crrev.com/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d/chrome/browser/vr/elements/ui_element_name.cc
[modify] https://crrev.com/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d/chrome/browser/vr/elements/ui_element_name.h
[modify] https://crrev.com/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d/chrome/browser/vr/model/color_scheme.cc
[modify] https://crrev.com/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d/chrome/browser/vr/model/color_scheme.h
[modify] https://crrev.com/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d/chrome/browser/vr/testapp/vr_test_context.cc
[modify] https://crrev.com/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d/chrome/browser/vr/ui_scene.cc
[modify] https://crrev.com/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d/chrome/browser/vr/ui_scene.h
[modify] https://crrev.com/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d/chrome/browser/vr/ui_scene_constants.h
[modify] https://crrev.com/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d/chrome/browser/vr/ui_scene_creator.cc
[modify] https://crrev.com/618bf8fcfac14a5c3ff82b9b5d06432d792cdd8d/chrome/browser/vr/ui_unittest.cc

Actually, updating this to WontFix since we're no longer taking this approach for repositioning.

(facepalm), wrong again! Sorry for the churn.

While you're moving the content window, "rolling" refers to tipping your head from side to side so that your ears get closer to your shoulders. Our repositioning code currently reorients the content window so that it's pointing "up" with respect to your head. So if you tilt your head from side to side, the content window will tilt with you. But say you tilt by just a few degrees and then stop positioning the window. Now you're in a situation where the content window is skewed with respect to the horizon. Kinda like a picture that's not hung level on the wall. 

Ian is there work left to land in M66?  If not please deprioritize and/or move to a future milestone.

Verified with build 66.0.3359.10.