For inclusion of Sleep

BUG=angleproject:892

Change-Id: I1a9491102e9943d945eef0ba372a6779c30cd311
Reviewed-on: https://chromium-review.googlesource.com/273131Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Corentin Wallez <cwallez@chromium.org>