Make exportMetrics strict
Make exportMetrics strict

Summary: _typescript_

Reviewed By: danielbuechele

Differential Revision: D17074932

fbshipit-source-id: 1a6a8e81a9d15021dd9b51a0c3a394a2cf349e9c

facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper