webkitfullscreenchange event for iFrame

/* works on all elements except iframes */
document.addEventListener("webkitfullscreenchange", function() {
   alert("hello world");
}, false); 
/* never triggers even when iFrame enters full screen */
myIframe.addEventListener("webkitfullscreenchange", function() {
   alert("hello iframe");
}, false);

我无法获得事件监听器webkitfullscreenchange事件触发iframes。iFrame在同一个原点下。有人知道怎么做吗?谢谢。