Summary:
#changelog: [internal]
When I built ThreadStorage I didn't know about existence of `thread_local` keyword. Because it achieves the same goal, using built in c++ features is preferred over building our own.
Reviewed By: JoshuaGross, shergin
Differential Revision: D24380680
fbshipit-source-id: e961fc34c6d3f085fc9b918b20bb4827de0d5624