Undo bogus change to use old dart:io API.

Undo bogus change to use old dart:io API.

Committed: https://code.google.com/p/dart/source/detail?r=14928

[Bob Nystrom, 2012-11-14 23:29:34]

Apparently I had an out-of-date editor, so when I fixed this warning, I actually
fixed it to the wrong older API. The previous code was correct.

TBR.

[nweiz, 2012-11-14 23:31:45]

On 2012/11/14 23:29:34, Bob Nystrom wrote:
> Apparently I had an out-of-date editor, so when I fixed this warning, I
actually
> fixed it to the wrong older API. The previous code was correct.
> 
> TBR.

Oh, yeah, I made that mistake myself a while ago. Unfortunately I also couldn't
remember which way was correct while reviewing :p.