R1:d8318089c85e

Fix super long topics in Conpherence header

Summary: Add some ellipsis if the topic is absurdly long.

Test Plan: desktop, mobile, tablet. MMMMMMMmmmMMMMMMmMMMmMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D16718