Fix redundant scrollbar on Firefox.  Previously both the toolbox and the scrollbars resized by hooking the resize event.  This caused a race condition allowing the scrollbar to sometimes resize before the toolbox.  Now the scrollbar's resize is hardcoded after its container has resized.

Review URL: https://codereview.appspot.com/12002045

git-svn-id: http://blockly.googlecode.com/svn/trunk@1158 c400ca83-b69d-9dd7-9705-49c6b8615e23