WPT import https://crrev.com/c/1185286 introduced new failures in external/wpt/webxr:

List of new failures:
external/wpt/webxr/xrSession_requestAnimationFrame_getDevicePose.https.html new failing tests: https://crrev.com/c/1185286/4/third_party/WebKit/LayoutTests/external/wpt/webxr/xrSession_requestAnimationFrame_getDevicePose.https-expected.txt
[ Mac10.12 ] external/wpt/webxr/xrSession_requestAnimationFrame_getDevicePose.https.html [ Failure Timeout ]

This import contains upstream changes from d2fa1bdc90e7a56f16f28d096de3a6c22f711033 to 61aa8d06ff3cf42179dc08c63e65dbbd3127762f:
Serialize clip-path and shape-outside using Servo.: https://github.com/web-platform-tests/wpt/commit/61aa8d06ff3cf42179dc08c63e65dbbd3127762f
Add bounds check tests for WebDriver pause action.: https://github.com/web-platform-tests/wpt/commit/0f2cd7fc8f9d84fdd2cd2c31728e181dd70ca0db
XHR: Split up xmlhttprequest-timeout-worker-synconworker.html: https://github.com/web-platform-tests/wpt/commit/2e969bc4381dd98e7e0862b40561136d87d58dfe
HTML: test that floating legends do not disappear: https://github.com/web-platform-tests/wpt/commit/ef8f70b61f3234b71f5b0872859bba744696d1eb
Split up editing/run/* with `variant`: https://github.com/web-platform-tests/wpt/commit/8587af6ad0745be630e30a819418581ddd53b631
Merge pull request #12266 from bocoup/fix-timeout-client-hints: https://github.com/web-platform-tests/wpt/commit/3c8cb3edc5ddbe2dba11ea694f07c8aeb2c36ee2
Merge pull request #12619 from web-platform-tests/zcorpan/fieldset-overflow-hidden: https://github.com/web-platform-tests/wpt/commit/6bfd897c272148313895b0a6a72ed7a4da6f52e4
HTML: test fieldset with overflow: hidden: https://github.com/web-platform-tests/wpt/commit/8572f9c8682ca493e3afd1392e301844ecccf94c
[client-hints] Detect errors to avoid timeouts: https://github.com/web-platform-tests/wpt/commit/d2f36ed80d50515797b780fe6b36ab6219526970