test: expand issue7863 test
test: expand issue7863 test

This was sitting in my client but I forgot hg add.

LGTM=bradfitz
R=bradfitz
CC=golang-codereviews
https://codereview.appspot.com/101800045

Committer: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang