WPT import https://crrev.com/c/1309874 introduced new failures in external/wpt/css/css-transforms:

List of new failures:
external/wpt/css/css-transforms/animation/list-interpolation.html new failing tests: https://crrev.com/c/1309874/4/third_party/WebKit/LayoutTests/external/wpt/css/css-transforms/animation/list-interpolation-expected.txt

This import contains upstream changes from 7b078f0d6ff82157c57f343838f61b5200686e53 to 9a317591796c107a6a591932d0233062526b094e:
Add a warning about runner issues (#13812): https://github.com/web-platform-tests/wpt/commit/9a317591796c107a6a591932d0233062526b094e
Check slot re-assignment for getComputedStyle.: https://github.com/web-platform-tests/wpt/commit/4b8cb25d91bc5961fd484a60be9c6c06b12ab744 [affecting this directory]
HTTP/Fetch: combining header values: https://github.com/web-platform-tests/wpt/commit/ba5fce6d64fcb0812ae23306b29721bb961c8d96
Update interfaces/IndexedDB.idl (#13810): https://github.com/web-platform-tests/wpt/commit/05689adeab8c97ad457011b6a1758cdfdad7bca8
Add tests for interpolating between mismatching rotate() functions where one has a zero angle: https://github.com/web-platform-tests/wpt/commit/7d0ccc0dfbe830d11a5eb8e7b0ebf4d3c4f51d8c [affecting this directory]
webdriver: remove ES6 construct from in-view center point tests (#13799): https://github.com/web-platform-tests/wpt/commit/b704e37ec97fe90b3a3d59c10f78c21907b5b576
Remove some suggested reviewers who have asked to be removed (#13796): https://github.com/web-platform-tests/wpt/commit/75b0f336c50105c6fea47ad253d57219dfa744d3 [affecting this directory]
Enable unified plan by default for Chrome Dev (#13795): https://github.com/web-platform-tests/wpt/commit/ced8eec6f128f8766a54ff767bd8db35c636b7fb
HTML: update innerText getter tests to return *inner* text: https://github.com/web-platform-tests/wpt/commit/cf0adc7f3d28a354913e252bc8c6228d699440ca
XMLHttpRequest: manipulate Content-Type less: https://github.com/web-platform-tests/wpt/commit/99f4fdcd906411c036e96c055e28b3e6ca84a1cc
IDBFactory databases flaky wpt fix.: https://github.com/web-platform-tests/wpt/commit/36ba2f8d72212ba48a47a3a45ad02c5d4773537c
Reimplementing getDatabaseNames() as databases() for indexeddb.: https://github.com/web-platform-tests/wpt/commit/7b94252585b28425f6cd01e691f85315519b4913
remove unused import: https://github.com/web-platform-tests/wpt/commit/3361ae5e8e8786ffced2d760785817bb51d05288
Restore seekable: https://github.com/web-platform-tests/wpt/commit/70abb3d310edc14a8ac91649271c77b8a9206217
Remove unused code in tools/wpt/utils.py: https://github.com/web-platform-tests/wpt/commit/a066f56ff24036e070391fc8527fe3538aab2219
Make one line-height the intrinsic block-size for <select> comboboxes.: https://github.com/web-platform-tests/wpt/commit/ae85077dcf1e0e58f379a6d731e99eca0eadfae5
Make empty <select>s have zero content-box inline-size, like in other UAs.: https://github.com/web-platform-tests/wpt/commit/dd6d752eae5be9b086181cae7a8f87c094d62f29
webdriver: add screenshot test utilities: https://github.com/web-platform-tests/wpt/commit/50bef2a7e7a9f49ae5e33b06f7845616e8da9808
webdriver: load wpt fixtures as pytest plugin: https://github.com/web-platform-tests/wpt/commit/2c830cddbc56cbe1320f8a71e3f4183757e2af06
webdriver: make wpt fixtures a module: https://github.com/web-platform-tests/wpt/commit/d5ff39c6fca6dacbca640e168a5eb61b7f510bb2
Add a reftest. (#13487): https://github.com/web-platform-tests/wpt/commit/6a0cd4be391da3d387d2cf9c112d893235a127cc [affecting this directory]
Call the tools/wpt/ tests simply "tests" (not "unittests") (#13782): https://github.com/web-platform-tests/wpt/commit/7452fbc120383dbfeae9759baeb9f2fe68cffc1f
[css-properties-values-api] Validate generate_property argument.: https://github.com/web-platform-tests/wpt/commit/add8843a7da2ab5ee5ba329c0ae052573c23cde2 [affecting this directory]
[css-properties-values-api] Test initial values individually.: https://github.com/web-platform-tests/wpt/commit/6014df860a812202756c59f230e9bfafb2c8332c [affecting this directory]
[css-properties-values-api] Test computed values individually.: https://github.com/web-platform-tests/wpt/commit/704a0dbc3dd38a81085b7b813b5602532a63cabd [affecting this directory]
Consistently use `manager` for ManagerGroup.pool entries (#13775): https://github.com/web-platform-tests/wpt/commit/8bb642da20e51c1e8cb8f8e23b1adeb444ab26ad
Indent `manager_group` method calls to within the `with` scope (#13778): https://github.com/web-platform-tests/wpt/commit/e2f346f20d1d165360ae7ca7df4b027113c217b0
Remove unused method `ManagerGroup.is_alive()` (#13777): https://github.com/web-platform-tests/wpt/commit/086f4ef0144b35ee125d1edfc478632b6885b1c7
[css-properties-values-api] Compute <resolution> values to 'dppx'.: https://github.com/web-platform-tests/wpt/commit/9d2432a20edd05076fa49f265adeeb64e78a3aba [affecting this directory]
Sync Mozilla CSS tests as of https://hg.mozilla.org/mozilla-central/rev/6e4537056d5363fc118fa946615955798892314b . (#13772): https://github.com/web-platform-tests/wpt/commit/1f06d26817ca7f03f3d42246fa1e14285e3aaecc [affecting this directory]
ServiceWorker: Move WPTs for ServiceWorkerContainer.startMessages() into its own file: https://github.com/web-platform-tests/wpt/commit/899e3a45f8d628c4a7cfb324e031a99f3a4aefdf
[css-properties-values-api] Compute <time> values to seconds.: https://github.com/web-platform-tests/wpt/commit/9082397e214eef1fd04e478e353cd0d19a64f040 [affecting this directory]
IndexedDB: More WPT tests for reading from autoincrement stores.: https://github.com/web-platform-tests/wpt/commit/2b3f736e9874c92cef6d296a7b455c5b8dd4fc9a