This shaves a fair amount of time of stylist rebuild.
Most of the extra remaining overhead are memory allocations...
I'll try to get those sorted out next, though fixing that may overlap quite a
bit with the work Cameron is doing in bug 1382925.
Source-Repo: https://github.com/servo/servo
Source-Revision: b11b65837930fff7ec793e935af46d7edbeccda5
--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : 5c506863db85090b1edb2dcd4350a6913cf4cf21