add side window tracking area only once for visible rect and let AppKit update it
add side window tracking area only once for visible rect and let AppKit update it

git-svn-id: cb3fc60f0f557b927b8032d8a94e869b6f9f230b@6102 0fceea05-a30d-0410-8a8b-80ef821fb0a1

camillobruni/skim,camillobruni/skim,camillobruni/skim,jasongrout/skim,jasongrout/skim,camillobruni/skim