R1:68fa70eacbc8

Make images work in the unified diff view

Summary: Ref T2009. Still a touch glitch-ish but essentially functional now.

Test Plan: Viewed image diffs in 1up and 2up views. Made inline comments on them.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T2009

Differential Revision: https://secure.phabricator.com/D12003