Updates golang/go#27992

Change-Id: Ic327df7cc5002a3d537f9117559c25f30e1eab9c
Reviewed-on: https://go-review.googlesource.com/c/151799
Run-TryBot: Andrew Bonventre <andybons@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>