phutil_utf8_shorten => PhutilUTF8StringTruncator
Summary: Ref T3307. Very easy
Test Plan: this very diff!
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: epriestley, Korvin
Maniphest Tasks: T3307
Differential Revision: https://secure.phabricator.com/D10391