GitLab

As following the spec[1] at XRView, The eye has changed to use XREye
instead of VREye. And it is nullable.

[1] : https://immersive-web.github.io/webxr/#xrview-interface

Bug: None
Cq-Include-Trybots: luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: Ib8e698f714ea107bc0ac9a275a6466d419a067e3
Reviewed-on: https://chromium-review.googlesource.com/1180629Reviewed-by: Brandon Jones <bajones@chromium.org>
Commit-Queue: Byoungkwon Ko <codeimpl@gmail.com>
Cr-Commit-Position: refs/heads/master@{#584656}