Fix build failure on WinRT due to missing Sleep definition. Change-Id: I9032484dde6e690fcd175d6d76192724e5bc0357 Reviewed-on: https://chromium-review.googlesource.com/225893 Reviewed-by: Cooper Partin <coopp@microsoft.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>