Display blame colors in multiline highlighting

Summary:
Multiline highlighting didn't work well together with blame.

Blame Rev: rPe24a6ac

Test Plan: /diffusion/...$596-598?view=blame

Reviewers: epriestley

Reviewed By: epriestley

CC: Koolvin, aran, epriestley

Differential Revision: https://secure.phabricator.com/D1814