Cleans up the mobile web app sample for 2.4.

Review at http://gwt-code-reviews.appspot.com/1468801

Review by: jlabanca@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@10358 8db76d5a-ed1c-0410-87a9-c151d255dfc7