Summary: Nobody knows that it's possible to highlight more lines because there's no interface for it.
Test Plan:
Highlighted:
- single line
- top to bottom
- bottom to top
- inside to outside
Reviewers: Korvin, epriestley
Reviewed By: epriestley
CC: aran, epriestley
Differential Revision: https://secure.phabricator.com/D3150
