[Nautilus-list] I made another cut at improving speed

[Darin Adler <darin bentspoon com>]

I now understand the main reason Nautilus on HEAD is slower than 1.0.4.

The new desktop link feature requires looking into each directory to see if
there's a .desktop file in there. And doing this with Nautilus's async.
machinery seems to be rather slow. It's probably easy to speed this up by
getting the information for lots of files with a single async. call. But I
didn't do that today.

Rather than tackle this problem or figure out a new design, I decided to
first fix as many of the bugs as possible.

I fixed a number of bugs with the way the directory view was waiting for the
load to be complete. Confusion about whether the load is finished when the
directory load part is done, or whether you have to wait, made things much
slower than they needed to be. This also accounts for the small number of
files appearing at first, then the bulk of them appearing 4 seconds later.

So after my commit today, things should be faster, but I think they will be
yet faster after we fix it so there's not a separate async. call for each
directory.

Perhaps we can get to "good enough for a 1.0.5 release" soon.

    -- Darin