Got an UiBinder useSafeHtmlTemplates warning on GWT compiling

When I was running a sample MVP application of GWT , show an error

[WARN] [helloMVP] Configuration property UiBinder.useSafeHtmlTemplates is false! UiBinder SafeHtml integration is off,
leaving your users more vulnerable to cross-site scripting attacks. This property will default to true in future releases of GWT

Solution is add one line in Contacts.gwt.xml