Added test file.

For #18130.

Change-Id: Ifcfd7cd1acf9dd6a2f4f3d85979d232bb6b8c6b1
Reviewed-on: https://go-review.googlesource.com/34988
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>