Fixes TreeMap's iterator which currently can get jacked up when doing removals.

Found by: jat
Suggested by: bruce
Patch by: scottb (+rdayal)
Review by: rdayal (desk)


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@2928 8db76d5a-ed1c-0410-87a9-c151d255dfc7