Properly update the icon data before placing the icon, because
positioning might depend on full icon contents on the desktop, whereas
updating contents don't care about position.

When an icon position overflows the desktop area, it is clamped to stay
in the visible area, but this computation depends on accurate icon and
label sizes, which is only available when the icon is fully loaded.

Fix the code to first load the contents and then position instead of
the other way around, which was actually trivial.

Note that visible positions were most often correct anyway for two
reasons:

1. Most of the time icons do not overflow, as they are positioned on
   the final desktop size anyway.  It however can easily happen
   reducing monitor resolution or increasing desktop view zoom.
2. A second layout pass happens most of the time (I'm not yet sure why
   and when though), but not when an update is triggered before the
   previous one terminated (e.g. quickly hitting F5 twice).