Updates golang/go#20448

Change-Id: I6366b0b0b36d81095ab347ca35e1e72169c05c15
Reviewed-on: https://go-review.googlesource.com/43853
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tom Bergan <tombergan@google.com>