Per comment on CL 120316.

Updates #25280

Change-Id: I7d078de4030bd10934468e04ff696a34749bd454
Reviewed-on: https://go-review.googlesource.com/c/153500
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Rob Pike <r@golang.org>