Disable failing WebXR tests

Disables failing WebXR tests that are causing CQ issues. Will be
re-enabled once the root cause is found and fixed.

TBR=billorr@chromium.org

Bug: 913161
Change-Id: If50af30cc9e24ce917989a0b0ac210254ce503bb
Reviewed-on: https://chromium-review.googlesource.com/c/1372540
Reviewed-by: Brian Sheedy <bsheedy@chromium.org>
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615670}
2 files changed