Import wpt@a6c717293ac291bd8085ede7af88717141d6ee69

https://github.com/web-platform-tests/wpt/compare/db9f0ab6e...a6c717293

Using wpt-import in Chromium 4cd21c9009163dbccbf545d9e7bcfc6d2a782360.
With Chromium commits locally applied on WPT:
  4c883e5e24 "Fix wpt flaky tests"
  a5048548de "[layout] 2 tests for stretch keyword"

Note to gardeners: This CL imports external tests and adds expectations
for those tests; if this CL is large and causes a few new failures,
please fix the failures by adding new lines to TestExpectations rather
than reverting. See:
https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md

Directory owners for changes in this CL:
bjonesbe@adobe.com:
  external/wpt/css/css-shapes
cbiesinger@chromium.org:
  external/wpt/css/css-sizing

NOAUTOREVERT=true
R=rubber-stamper@appspot.gserviceaccount.com

No-Export: true
Cq-Include-Trybots: luci.chromium.try:linux-blink-rel
Change-Id: I69d20862c537acff6bb9d9f7150e991ce12bc228
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5995490
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: WPT Autoroller <wpt-autoroller@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1378720}