For #27539.

Change-Id: I0e27f142224e820205fb0e65ad03be7eba93da14
Reviewed-on: https://go-review.googlesource.com/c/146999
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>