R1:6337fa99a3ab

Render description changes in countdown timeline

Summary: Renders standard description was changed timeline transaction in Countdown

Test Plan: Edit Description, see transaction and change dialog.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D13711