This continues #305 Changelog: - Upstream: https://github.com/servo/stylo/compare/7cd2a178d3c3ea1a8a88a6af211c0a0e6233c9fe...74ddab409140ff5f47e3f80a8c2aa26d9745fd90 - Servo fixups: https://github.com/servo/stylo/compare/a5eabbdfc294e42c9cb9dab0aace7c6cbcb1ad97...ecf17b54251b2f380a186780811f3c234308f57d Servo PR: https://github.com/servo/servo/pull/43045
