Updates #12580

Change-Id: I9f9578148ef2b48dffede1007317032d39f6af55
Reviewed-on: https://go-review.googlesource.com/22191Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Tom Bergan <tombergan@google.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>