This is #7154 with two additional commits (that I did rather than ask @zentner-kyle to do it because it was a bit tricky.)
r? @pcwalton for the last two commit
r=me+pcwalton in #7154 for earlier commits.
Source-Repo: https://github.com/servo/servo
Source-Revision: 5e83a3f0a3bab226cca849ab33fa3322ef71813d