Support PhabricatorSpacesInterface in ApplicationSearch UI
Summary: Ref T8441. Does what it says, provided other conditions (like using the new SearchField stuff) are fulfilled.
Test Plan:
{F473836}
{F473837}
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T8441
Differential Revision: https://secure.phabricator.com/D13171