For #17540.

Change-Id: Ie01f39797526934fa553f4279cbde6c7cbf14154
Reviewed-on: https://go-review.googlesource.com/36854Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>