Updates #21196

Change-Id: I307cacc963448b90a23f633bec15498ba7bf1937
Reviewed-on: https://go-review.googlesource.com/53356
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>