AbstractAjaxTimerBehavior fails to trigger in some circumstances. Wicket.Event.add is called to trigger Wicket.Timer.set on the load event. The code in Wicket.Event.add adds a domready listener, which registers the onload listener as soon as the dom is ready. However, the browser fires onload before it fires domready, therefore the registered listener is never triggered and Wicket.Timer.set is not called.
I'm not sure if this behavior is specific to recent versions of Google Chrome, but it happens quite consistently (but not always). I think a special case for onload is needed: