Write should return ErrWriteAfterClose instead
of ErrWriteTooLong when called after Close.
Change-Id: If5ec4ef924e4c56489e0d426976f7e5fad79be9b
Reviewed-on: https://go-review.googlesource.com/9259
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>
