add timer to track how long the re-ordering takes
add timer to track how long the re-ordering takes

Summary: As in the title.

Reviewed By: NTillmann

Differential Revision: D33941712

fbshipit-source-id: 939761a4c374bd51930a22a0297d6bdc3038332f

facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex,facebook/redex