For #14876.

Change-Id: I0992859264cbaf9c9b691fad53345bbb01b4cf3b
Reviewed-on: https://go-review.googlesource.com/21085Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>