Updates golang/go#15167

Change-Id: I58bd7e4e6ba88a2ffba11506e5ac0495de303b5b
Reviewed-on: https://go-review.googlesource.com/23023Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>