This continues #200

Changes are on the upgrade branch

Changelog:

• No-op change because of Use firefox repo as upstream #186: https://github.com/servo/stylo/compare/7e2201c32c991d20faaf05a67aaee2c715361e8e..0a5440a8afa32501c27c9eca4deea9bc4f04772d
• Upstream: 0a5440a...fe9eadf
• Servo fixups: e8dbccb...31a2c9c

Servo PR: servo/servo#37822