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>

webfd/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,bryanxu/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,d0f/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,webfd/go-zh,bryanxu/go-zh,d0f/go-zh,webfd/go-zh,sanjosh/sanjos100-tipc,d0f/go-zh,bryanxu/go-zh,d0f/go-zh,sanjosh/sanjos100-tipc,bryanxu/go-zh,bryanxu/go-zh,d0f/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,webfd/go-zh,webfd/go-zh,d0f/go-zh,d0f/go-zh,webfd/go-zh,d0f/go-zh,bryanxu/go-zh