WPT import https://crrev.com/c/1417410 introduced new failures in external/wpt/webrtc:

List of new failures:
[ Win7 ] virtual/webrtc-wpt-unified-plan/external/wpt/webrtc/RTCPeerConnection-track-stats.https.html new failing tests: https://crrev.com/c/1417410/4/third_party/blink/web_tests/platform/win7/virtual/webrtc-wpt-unified-plan/external/wpt/webrtc/RTCPeerConnection-track-stats.https-expected.txt

This import contains upstream changes from 584bdfaebda852482e349f3632ac25680e64ace4 to cd94eba6eca288f9d8862ef822c5f9957c8de343:
[css-overflow] property parsing and serialization (#14910): https://github.com/web-platform-tests/wpt/commit/cd94eba6eca288f9d8862ef822c5f9957c8de343
service worker: WPT: Add generated response tests for XHR response URL.: https://github.com/web-platform-tests/wpt/commit/938f940a19fc23db96248d843076929f9a035f2b
Fix numerical inaccuracy in background-size auto: https://github.com/web-platform-tests/wpt/commit/b01839aa6b032b70ec7ead85f6ef73bbbe5d3b12
service worker: WPT: Add test for XHR Document's URL.: https://github.com/web-platform-tests/wpt/commit/f304798b6ec918d01d32cb3879ca714211ea8be4
Portals: Add a WindowEventHandler to the PortalActivateEvent.: https://github.com/web-platform-tests/wpt/commit/2ade7dc478df87727880d849a76ee4b5be058f63