1. @DomName('FetchEvent.respondWith')
  2. @DocsEditable()
  3. @Experimental()
void respondWith(Future r)

Source 

@DomName('FetchEvent.respondWith')
@DocsEditable()
@Experimental() // untriaged
void respondWith(Future r) =>
    _blink.BlinkFetchEvent.instance.respondWith_Callback_1_(this, r);