Update #12815

Change-Id: I3bf6de74bc8ab07000fe9a4308299839ef20632f
Reviewed-on: https://go-review.googlesource.com/15283Reviewed-by: Evan Brown <evanbrown@google.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>