The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27

commit 4f28a8f0e9f22e6a2d70df4a885c8be315af8d27
Author: Bill Orr <billorr@chromium.org>
Date: Tue Jul 03 06:54:32 2018

Add browser test for WebXR that validates textures use the expected pose

The page encodes a frame id into the clear color, clears the texture, then submits it.

The test then reads the frame id, and validates that the pose used was the expected pose used.

The test found an issue where frames would be submitted after getting the next frame's pose,
causing extra latency and worse reprojection.  This is fixed as part of the change so the test
passes.

BUG:  854309 ,  850165 ,  801034 
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: I0f891e9929d4a0427c74ae137ed2a9c31d7744cd
Reviewed-on: https://chromium-review.googlesource.com/1123228
Commit-Queue: Bill Orr <billorr@chromium.org>
Reviewed-by: Brian Sheedy <bsheedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572130}
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/chrome/browser/vr/test/mock_openvr_device_hook_base.cc
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/chrome/browser/vr/test/mock_openvr_device_hook_base.h
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/chrome/browser/vr/test/vr_xr_browser_test.cc
[add] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/chrome/browser/vr/webvr_frame_pose_browser_test.cc
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/chrome/test/BUILD.gn
[add] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/chrome/test/data/vr/e2e_test_files/html/test_webxr_poses.html
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/chrome/test/data/vr/e2e_test_files/resources/webvr_boilerplate.js
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/chrome/test/data/vr/e2e_test_files/resources/webxr_boilerplate.js
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/device/vr/oculus/oculus_render_loop.cc
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/device/vr/oculus/oculus_render_loop.h
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/device/vr/openvr/openvr_device_provider.cc
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/device/vr/openvr/openvr_render_loop.cc
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/device/vr/openvr/openvr_render_loop.h
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/device/vr/openvr/test/fake_openvr_impl_api.cc
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/device/vr/openvr/test/test_helper.cc
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/device/vr/openvr/test/test_helper.h
[modify] https://crrev.com/4f28a8f0e9f22e6a2d70df4a885c8be315af8d27/device/vr/openvr/test/test_hook.h

Anna, please verify when you're back - it appears fixed to me, but its somewhat subtle.