Fix phone-ar test in webxr-samples

This change is needed to match the API change in
https://chromium-review.googlesource.com/c/chromium/src/+/1570217
but was missing in that CL.

TBR=bajones@chromium.org

Change-Id: Ic49436558c3cde7e42b9b8a4bd26c416f0b80f2b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1574457
Commit-Queue: Klaus Weidner <klausw@chromium.org>
Reviewed-by: Klaus Weidner <klausw@chromium.org>
Auto-Submit: Klaus Weidner <klausw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652689}
1 file changed