Sync Phabricator to Javelin HEAD

Summary: cpiro reported a cache inconsistency issue from a push a while ago
which this should fix (see #?????), and we haven't sync'd in a while anyway.

Test Plan: Poked some interfaces very gently.

Reviewers: cpiro, cpojer, tomo, jungejason, tuomaspelkonen, aran

Reviewed By: tomo

CC: aran, epriestley, tomo, cpiro

Differential Revision: 859