static/ext/src/data/flash/BinaryXhr.js
function () {
        var headers = [];
        Ext.Object.each(this.responseHeaders, function (name, value) {
            headers.push(name + ': ' + value);
        });
        return headers.join('\x0d\x0a');
    }
function () {
        var headers = [];
        Ext.Object.each(this.responseHeaders, function (name, value) {
            headers.push(name + ': ' + value);
        });
        return headers.join('\x0d\x0a');
    }
As in XMLHttpRequest.