HandlerRegistration reg1 = Event.addNativePreviewHandler(handler1);
assertFalse(Event.fireNativePreviewEvent(null));
handler0.assertIsFired(true);
handler1.assertIsFired(true);
reg0.removeHandler();
reg1.removeHandler();
}
/**
* Test that {@link Event#fireNativePreviewEvent(NativeEvent)} returns the
* correct value if the native event is prevented from being canceled, even if