解决HTTPS嵌套HTTP的问题

+function(){
    var a=document.createElement("meta");
    var b=document.createElement("meta");
    a.httpEquiv = "X-Webkit-CSP";
    b.httpEquiv = "Content-Security-Policy";
    a.content = b.content = "upgrade-insecure-requests";
    if(location.protocol==='https:'){
        document.head.insertAdjacentElement('afterbegin',b);
        document.head.insertAdjacentElement('afterbegin',a);
    }
}();