The tree table view has the scroll bar and the
"change visible columns", and these seem to be
non-idealy placed... there seem to be slight white
lines around the edges, for example (compare with,
say, the source editor where these white borders
don't exist).

I think it would be good if someone from the
visual design area were to look at this and
suggest fixes to make it look nicer.  Any issues
found should be filed in openide/explorer and good
if the subject is prefixed with [TTV]