R1:826e5405b611

Open files in very large diffs inline

Summary: This allows writing inline comments and reduces different behavior between normal and very large diffs.

Test Plan:
Verify that normal diff works.
Verify that very large diff works.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Koolvin

Differential Revision: https://secure.phabricator.com/D2361