Correctly compute chunk_file size and spans.
Correctly compute chunk_file size and spans.

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