private <W extends Widget & HasAllMediaHandlers> void verifyCanPlayThroughEventSink(W w) {
CanPlayThroughHandlerImpl handler = new CanPlayThroughHandlerImpl();
w.addCanPlayThroughHandler(handler);
assertFalse(handler.hasEventFired());
w.fireEvent(new CanPlayThroughEvent() {
});
assertTrue(handler.hasEventFired());
}