A test for CL 102036.

Change-Id: Ief6dcb4f478670813fbe22ea75a06815a4b201a3
Reviewed-on: https://go-review.googlesource.com/105875
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>