When drawing a very wide graph line diagram, smush it together a bit

Summary: Depends on D20345. Use a narrower layout for very large graphs to save some space.

Test Plan:
Before:

{F6320215}

After:

{F6320216}

This does not affect smaller graphs.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D20346