Rebase of #4175, closes #4175. r? @jdm Source-Repo: https://github.com/servo/servo Source-Revision: 8759d42559bc5c10f8d90903f33f75bddf44d9fe
Rebase of #4175, closes #4175. r? @jdm Source-Repo: https://github.com/servo/servo Source-Revision: 8759d42559bc5c10f8d90903f33f75bddf44d9fe