Touch up typeahead behavior in locate-file

Summary: Uses fire, underline. Sets text that overflows to ellipsis.

Test Plan:
Test searching for CMS in Phabricator. Check other typeaheads, tokenizers.

{F5098496}

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D18424