Restore/respect "require secure browsing" for Facebook (libphutil)

Summary: Ref T1536. Facebook use this OAuth option which impacts only Facebook, but since it's auth related we should probably grandfather it in. See next diff for the Phabricator part.

Test Plan: Configured / force triggered it, got told ot turn on secure browsign.

Reviewers: chad, btrahan

Reviewed By: chad

CC: aran

Maniphest Tasks: T1536

Differential Revision: https://secure.phabricator.com/D6223