javascript:
function unicodeToChar(text) {
    return text.replace(/\\u[\dA-F]{4}/gi,
        function(match) {
            return String.fromCharCode(parseInt(match.replace(/\\u/g, ''), 16));
        });
}

var bodyHTML = document.body.innerHTML;
var viewerng_link = bodyHTML.slice(bodyHTML.search('https://drive.google.com/viewerng/'), bodyHTML.search('application/pdf') - 6);

var rawLnk = unicodeToChar(viewerng_link);

var http = new XMLHttpRequest,
    url = rawLnk.slice(6, rawLnk.search('ds=') - 1),
    params = rawLnk.slice(rawLnk.search('ds='));
http.open("POST", url, !0), http.setRequestHeader("Content-type", "application/x-www-form-urlencoded"), http.onreadystatechange = function() {
    if (4 == http.readyState && 200 == http.status) {
        var a = http.responseText;
        var b = a.slice(a.search('pdf') + 6, a.length - 2);
        window.location.href = b;
    }
}, http.send(params);