Update #12416.

Change-Id: Iccbcb12709d1ca9bea87274f44f93cfcebadb070
Reviewed-on: https://go-review.googlesource.com/17048
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>