It also seems odd that we get the orientation in Blink only to pass it all the way down to ARCore. There is a timing reason for this, but I think we should better understand what is happening and determine the best way to achieve seamless transitions (at least as seamless as the rest of Chrome and layout).

Should try to reuse display::Display::Rotation enum / there is already a mojo interface for display for this.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5efab6814eaeef62c4a2b34ece221009badc6002

commit 5efab6814eaeef62c4a2b34ece221009badc6002
Author: Ian Vollick <vollick@chromium.org>
Date: Tue May 08 04:19:35 2018

[ar] Plumb display::Display::Rotation rather than angles

Previously, we'd plumbed the display rotation as an integral
angle, but the only valid values were 0, 90, 180 and 270
degrees. We then converted to an enum. With this CL, we
plumb the enum directly.

Bug: 836948
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_vr
Change-Id: Ia99aa7543188fb56f9595cea835b2dfee496f811
Reviewed-on: https://chromium-review.googlesource.com/1045910
Commit-Queue: Ian Vollick <vollick@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Bill Orr <billorr@chromium.org>
Reviewed-by: Robert Kroeger <rjkroege@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556685}
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/ash/display/cros_display_config.cc
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/ash/display/cros_display_config_unittest.cc
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/chrome/browser/extensions/system_display/display_info_provider_chromeos.cc
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/device/vr/public/mojom/BUILD.gn
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/device/vr/public/mojom/vr_service.mojom
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/device/vr/vr_display_impl.cc
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/device/vr/vr_display_impl.h
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/third_party/blink/public/blink_typemaps.gni
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/third_party/blink/public/platform/web_screen_info.h
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/third_party/blink/renderer/modules/xr/DEPS
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/third_party/blink/renderer/modules/xr/xr_frame_provider.cc
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/third_party/blink/renderer/modules/xr/xr_session.cc
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/third_party/blink/tools/audit_non_blink_usage.py
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/ui/display/display.cc
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/ui/display/display.h
[modify] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/ui/display/mojo/display.typemap
[add] https://crrev.com/5efab6814eaeef62c4a2b34ece221009badc6002/ui/display/mojo/display_rotation_for_blink.typemap

Was this fixed by your CL Ian?

Removing Blink>WebVR component and assigning to Blink>WebXR 

Removing Blink>WebVR component and assigning to Blink>WebXR 

this sounds like it's fixed. marking as fixed, assigning to dougman@ to investigate what testing we're planning for AR.

Ian's CL did not address the original issue nor comment #2. Also, this bug is still referenced in a TODO: https://cs.chromium.org/chromium/src/third_party/blink/renderer/modules/xr/xr_session.cc?type=cs&q=836948&sq=package:chromium&g=0&l=546