Fix an issue where "Close Revision" did not appear in the UI

Summary:
Ref T2543. When called from the UI to build the dropdown, there's no Editor, since we aren't actually in an edit flow.

This logic worked for actually performing the edits, just not for getting the option into the dropdown.

Test Plan: Used the dropdown to close an "Accepted" revision which I authored.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T2543

Differential Revision: https://secure.phabricator.com/D18490