Fixes List.subList problems.

Public review at: http://gwt-code-reviews.appspot.com/620802/show

Issue: 4993
Patch by: markovuksanovic@gmail.com
Review by: jat, rice


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@8308 8db76d5a-ed1c-0410-87a9-c151d255dfc7