We shouldn't be spinning up the devices until requestSession() is called. Maybe that's not currently the case. Even then, it's probably possible for multiple requestSession() calls to come in while initialization has already been requested.

[I deleted my Comment 3 because it was incorrect.]

The work to address Comment 1 is tracked by issue 849568.

I'll try to tackle this early next week, since it may be causing real issues.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7a32f749ecae1923fda1485aa423b8e46dafddcf

commit 7a32f749ecae1923fda1485aa423b8e46dafddcf
Author: Anna Offenwanger <offenwanger@chromium.org>
Date: Thu Jul 12 17:13:22 2018

Modify XRSession so that session geometry is only sent when it changes

Making it so that instead of receiving geometry every frame, ar_core
only gets geometry (frame size and rotation) when it changes. This saves
some processing every frame, and allows the GetFrameData interface to be
made uniform for AR and VR.

Bug:  856259 ,846521
Change-Id: I5828f57e1292f932c68148ac1e6b898f966b8d00
Reviewed-on: https://chromium-review.googlesource.com/1115776
Commit-Queue: Anna Offenwanger <offenwanger@chromium.org>
Reviewed-by: Bill Orr <billorr@chromium.org>
Reviewed-by: Klaus Weidner <klausw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574611}
[modify] https://crrev.com/7a32f749ecae1923fda1485aa423b8e46dafddcf/chrome/browser/android/vr/arcore_device/arcore_device.cc
[modify] https://crrev.com/7a32f749ecae1923fda1485aa423b8e46dafddcf/chrome/browser/android/vr/arcore_device/arcore_device.h
[modify] https://crrev.com/7a32f749ecae1923fda1485aa423b8e46dafddcf/chrome/browser/android/vr/arcore_device/arcore_gl.cc
[modify] https://crrev.com/7a32f749ecae1923fda1485aa423b8e46dafddcf/chrome/browser/android/vr/arcore_device/arcore_gl.h
[modify] https://crrev.com/7a32f749ecae1923fda1485aa423b8e46dafddcf/device/vr/vr_device_base.cc
[modify] https://crrev.com/7a32f749ecae1923fda1485aa423b8e46dafddcf/device/vr/vr_device_base.h
[modify] https://crrev.com/7a32f749ecae1923fda1485aa423b8e46dafddcf/device/vr/vr_display_impl.cc
[modify] https://crrev.com/7a32f749ecae1923fda1485aa423b8e46dafddcf/device/vr/vr_display_impl.h
[modify] https://crrev.com/7a32f749ecae1923fda1485aa423b8e46dafddcf/third_party/blink/renderer/modules/xr/xr_frame_provider.cc
[modify] https://crrev.com/7a32f749ecae1923fda1485aa423b8e46dafddcf/third_party/blink/renderer/modules/xr/xr_frame_provider.h
[modify] https://crrev.com/7a32f749ecae1923fda1485aa423b8e46dafddcf/third_party/blink/renderer/modules/xr/xr_session.cc
[modify] https://crrev.com/7a32f749ecae1923fda1485aa423b8e46dafddcf/third_party/blink/renderer/modules/xr/xr_session.h

Removing Blink>WebVR component and assigning to Blink>WebXR 

Removing Blink>WebVR component and assigning to Blink>WebXR 

over to @lincolnfrog to take another look.