This makes the dependency tracker properly recurse into simple selectors inside the current complex selector to find the appropriate dependencies.
We can't still remove the outer visitor because we need it for stuff like `:not(.foo + bar)`, but I plan to get rid of it in a followup as long as try comes back green.
Source-Repo: https://github.com/servo/servo
Source-Revision: 53c47acfc425ac2dcc5d8aa08d4882c4bb0e7251
Also refactors a lot of the restyle hint code to use these new hooks, and removes a lot of hacks in servo that shouldn't be needed because of correct handling of restyles due to attribute changes.
I just smoketested this, so going for a full try run now.
Source-Repo: https://github.com/servo/servo
Source-Revision: 949931ec0caa20b9f38a12863f610da562950b90