Removed the private content field from DisclosurePanel and instead deferred to the SimplePanel that contains the content Widget. These prevents a bug when the content is removed from the DisclosurePanel using Widget#removeFromParent(). Patch by: jlabanca Review by: ecc Issue: 2792 git-svn-id: https://google-web-toolkit.googlecode.com/svn/releases/1.6@4336 8db76d5a-ed1c-0410-87a9-c151d255dfc7