Updates #21487

Change-Id: Ia549a87a8a305cc80da11ea9bd904402f1a14689
Reviewed-on: https://go-review.googlesource.com/56321Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>