Allows UiRenderer styles before the first call to render()

Fields are initialized both upon construction and on a call to render()

Also ensured that ui:with fields never get optimized as final.

Review at http://gwt-code-reviews.appspot.com/1794803


git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@11231 8db76d5a-ed1c-0410-87a9-c151d255dfc7