ble-type"><a href="polymer_app_layout/HttpRequestUpload-class.html">HttpRequestUpload</a></span>
                <a href="polymer_app_layout/HttpRequest/upload.html">upload</a>
            </dt>
            <dd>
                <div class="readable-writable">
        read-only
    </div>
    <code class="prettyprint lang-dart">EventTarget</code> that can hold listeners to track the progress of the request.
The events fired will be members of <code class="prettyprint lang-dart">HttpRequestUploadEvents</code>