Summary: title

Test Plan: unit

Reviewed By: hans@fb.com

Subscribers: folly-diffs@, jsedgwick, yfeldblum, chalfant, hannesr, vloh

FB internal diff: D1984864

Tasks: 6045789

Signature: t1:1984864:1429116418:b4a9cdbb88f605a09b5753eea41dd970c96b9d4e