Fix for issue 4532. Removes the CSS expressions from PopupImplIE6 that were interfering with layout on IE7. Review at http://gwt-code-reviews.appspot.com/238801 git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@7745 8db76d5a-ed1c-0410-87a9-c151d255dfc7