Added some comments on lines that confused me.
Removed redundant resize on scroll. If this is a browser compatibility issue (maybe browser X fires scroll preemptively) let me know and I'll add a comment.

R=neil.fraser@gmail.com

Review URL: https://codereview.appspot.com/12537044

git-svn-id: http://blockly.googlecode.com/svn/trunk@1188 c400ca83-b69d-9dd7-9705-49c6b8615e23