[LayaAir 2.0]Laya内嵌iframe预览时不显示网页，编辑器和开发者工具上没问题

this.iframe = Laya.Browser.document.createElement("iframe");
        this.iframe.style.position ="absolute";//设置布局定位。这个不能少。
        this.iframe.style.zIndex = 1000;//设置层级
        this.iframe.style.left ="100px";
        this.iframe.style.top ="100px";
        this.iframe.src = "http://ask.layabox.com/";
        Laya.Browser.document.body.appendChild(this.iframe);