Update #15410

Change-Id: Iad3f2639aa7a67b11efc35a629e1893f7d87b957
Reviewed-on: https://go-review.googlesource.com/22430
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>