Crept into CL 9682, committed last week.

Change-Id: I5b8e9119dbfeb0bc3005623ab74dbd29311d17ae
Reviewed-on: https://go-review.googlesource.com/31814
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>