Used elem.textContent to set inner text on all standard browsers.  This is more efficient than the default method we implemented.
http://gwt-code-reviews.appspot.com/160805/show

Review by: jgw@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@7693 8db76d5a-ed1c-0410-87a9-c151d255dfc7