Keep track of which files each chunk contains lines from.
Keep track of which files each chunk contains lines from.

lekkas/livegrep,wfxiang08/livegrep,lekkas/livegrep,wfxiang08/livegrep,paulproteus/livegrep,lekkas/livegrep,lekkas/livegrep,paulproteus/livegrep,paulproteus/livegrep,paulproteus/livegrep,lekkas/livegrep,paulproteus/livegrep,lekkas/livegrep,wfxiang08/livegrep,wfxiang08/livegrep,paulproteus/livegrep,wfxiang08/livegrep,wfxiang08/livegrep