../../dart-html/Document-class.html">Document</a>, <a href="../../dart-html/Blob-class.html">Blob</a>, or json (also a
<a href="../../dart-core/String-class.html">String</a>). <code>null</code> indicates request failure.</p>
        </section>
                <section class="summary source-code" id="source">
          <h2><span>Implementation</span></h2>
          <pre class="language-dart"><code class="language-dart">@SupportedBrowser(SupportedBrowser.CHROME)
@SupportedBrowser(SupportedBrowser.FIREFOX)
@Su