WPT import https://crrev.com/c/1259943 introduced new failures in external/wpt/css:

List of new failures:
external/wpt/css/css-scroll-snap/inheritance.html new failing tests: https://crrev.com/c/1259943/4/third_party/WebKit/LayoutTests/external/wpt/css/css-scroll-snap/inheritance-expected.txt

This import contains upstream changes from f15449622a76d024c083ec481aa4269c955e7fec to a49e7638c45072077a92916ae41a26873e15d59a:
Python 3: Encode text content in Response.iter_content().: https://github.com/web-platform-tests/wpt/commit/a49e7638c45072077a92916ae41a26873e15d59a
Switch WebKit browser product to WebDriver executors (#13339): https://github.com/web-platform-tests/wpt/commit/dc97ad5a7865a4849678baf67c380a3cc7bb420b
Include ended tracks when cloning MediaStreams.: https://github.com/web-platform-tests/wpt/commit/425430423cbe2cc78a34b2e4732a0d4361052219
Remove and fix non-spec compliant WebRTC tests: https://github.com/web-platform-tests/wpt/commit/ca3d628ad63e6a1f4a818d6280dfb4aac344f6a7
Merge pull request #2103 from majido/scroll-restoration-order: https://github.com/web-platform-tests/wpt/commit/656382714083382c32a5e8df57a3fe07cb06b4b2
Use the voiceschanged event to wait for SpeechSynthesisVoice instance (#13017): https://github.com/web-platform-tests/wpt/commit/2d49b1ea2fb2c46765ef5bdb01e287497a7406a9
minor cleanup: https://github.com/web-platform-tests/wpt/commit/aafe9b958cdae4985724048ebb6d5cb6a4d18212
rewrite the test to match the spec change: https://github.com/web-platform-tests/wpt/commit/e08e5c19ac899159f7cb7622e982df64d5a7f500
Reland: Implement RTCIceTransport.onselectedcandidatepairchange: https://github.com/web-platform-tests/wpt/commit/efa4c0d1048c6f1e2aae98a8be295eea689fb6fe
AppCache: Add WPTs for AppCache on iframes: https://github.com/web-platform-tests/wpt/commit/5783f415ebbf2c9199f5d1b0b791fe425e61f57e
Align more closely with Gecko for clip-path reference box.: https://github.com/web-platform-tests/wpt/commit/123dbad2221a34797cd146cbaeaff50c04c6dded [affecting this directory]
Fix wpt/css/css-masking/mask-svg-content/mask-text-001.svg: https://github.com/web-platform-tests/wpt/commit/eaed217d2c3ed8250b585f5b56751e1d84b7e502 [affecting this directory]
Implement RTCQuicTransport.onquicstream and stream reset/finish: https://github.com/web-platform-tests/wpt/commit/2625aa78ed1abccb12cde20af2b5d6650a407cf6
sensors: Ensure a document without an associated frame does not crash: https://github.com/web-platform-tests/wpt/commit/27d87552c9a67481fb2d6ca82a71622c24ce7090
Remove invalid RTCPeerConnection.addTransceiver() tests: https://github.com/web-platform-tests/wpt/commit/f2a543c1a69fd7cd0fd772602fcfa7b85bb81f75
Update beacon WPTs: https://github.com/web-platform-tests/wpt/commit/597fc96b56d2160d60f204379b0d1d24f7e34578
Fix import of serve.serve in servo runner: https://github.com/web-platform-tests/wpt/commit/d0f60644eae1f6eda6c67390de1526d0231067f1
Minor style fixes: https://github.com/web-platform-tests/wpt/commit/507f6f5d863e97b3eb48ddf965ee3ecb3615a132
Add test to verify scroll restoration order in history traversal: https://github.com/web-platform-tests/wpt/commit/174b8518b95c1efcefa7f8ae8526178b8fdd846d
Python 3: Update some test expectations in test_pipes.py.: https://github.com/web-platform-tests/wpt/commit/97615176b59ada5216db3425d7c642be0e1e0f8d
Use the effective playback rate when calculating the playState: https://github.com/web-platform-tests/wpt/commit/24349cd332fa9bd97fdb73fe329b078fb5c4f15f
Tidy up tests in play-states.html a little: https://github.com/web-platform-tests/wpt/commit/4f33592a6137e91a74890a08f9fa445242a61a1f
wptserve: Add the application/wasm type to constants.content_types.: https://github.com/web-platform-tests/wpt/commit/30e50d2d618d01328c8afd82da42b89e4f59a87f
wptserve: Reformat and sort constants.content_types.: https://github.com/web-platform-tests/wpt/commit/1297dd3321f76fe508f3ed8b0edebd052e62cfa5
Add a test for incorrect content types in streaming WebAssembly methods.: https://github.com/web-platform-tests/wpt/commit/25a73a5105cc9b074b787cafbfe5ebe509065e84
Add interfaces/wasm-web-api.idl: https://github.com/web-platform-tests/wpt/commit/a5edd61ab252fd26dc29d248e5b8e583dc1ff908
Simplify UUID RegExp because OS variants: https://github.com/web-platform-tests/wpt/commit/7a564fd15ffbb61d61e65a32977e8349bdf3ec50
Update interfaces/payment-request.idl (#13328): https://github.com/web-platform-tests/wpt/commit/47288ef9f9c2ac6c2f978667dab9072f3bb968a4
Fix width of black <img> in multicol-span-none-001-ref.xht.: https://github.com/web-platform-tests/wpt/commit/679c8aba9e64c20e11bdd031f9ead4948da6dd8d [affecting this directory]
Make HasRTLChars() consider Hebrew presentation forms as RTL (again) and not consider U+FEFF as RTL (again).: https://github.com/web-platform-tests/wpt/commit/fec3928f355e049657d19780aa4b412d9d3a714b [affecting this directory]
Merge pull request #13319 from ewilligers/scroll-snap-inheritance: https://github.com/web-platform-tests/wpt/commit/ae452389fc4c04f275f84e2c884fece8af12eb90
Give all Travis jobs human-readable names (#13300): https://github.com/web-platform-tests/wpt/commit/00c4ce16393cd724edecef6ed5923056a5f370e0
XHR: enforce particular header line serialization: https://github.com/web-platform-tests/wpt/commit/47fdf656dd7d712766b5d6940ba7ee6ee052024e
[css-scroll-snap] Inheritance and initial values: https://github.com/web-platform-tests/wpt/commit/b5f378e220e54dfcb8d9540ed2c5159a17b48e03 [affecting this directory]