for CR9

blobDownloader.js

function downloadAsBlob () {
	var image = new XMLHttpRequest();
	image.open('GET', "http://www.google.si/images/logos/ps_logo2a_cp.png", true);
	image.responseType = "arraybuffer";
	image.onload = function(ev) {
	    var blob = new BlobBuilder();
	    blob.append(image .response);
	    var data = blob.getBlob();
            console.log(data.type, data.size)
	};
	image.send(null);
}

This code is from https://github.com/dz0ny/chrome-transmission-remote