SWT is not supporting 'latest' XULRunner.
See Bug 327696 – [Browser] implement support for xulrunner >= 4.0
See also The SWT FAQ, Q: How do I specify the default type of native renderer that is used by the Browser? or Q: How do I explicitly use Mozilla as the Browser's underlying renderer? or so.
For example,
- Download the last one which is available on eclipse from http://ftp.mozilla.org/pub/mozilla.org/xulrunner/releases/10.0.4esr/sdk/
- Extract it to C:\
- Edit your app's Run Configuration->Arguments->VM Arguments, add following argument. -Dorg.eclipse.swt.browser.XULRunnerPath=C:\xulrunner