servo: Merge #20603 - Run rustfmt on selectors, servo_arc, and style (from bholley:rustfmt_style); r=Manishearth

Now that rustfmt is getting close to stable, and work on the style system has died down a bit, it seemed like an opportune time to auto-format the style crates.

The first commit disables import reordering, since tidy and rustfmt don't currently agree on the correct ordering. The second commit does a bunch of manual fixups such that the output of rustfmt passes tidy. The third commit runs rustfmt on the three aforementioned crate.

There are a few dozen warnings in the style crate about lines longer than 100 characters. It would be good to fix these, but I don't have time for that now.

Source-Repo: https://github.com/servo/servo
Source-Revision: 9a900ef019cd643bff961d7b20db6da69f3edb29

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : 2b228d52a084bc832444ac686290840c4369f98d