If you can read JSON encoded HTTP headers of the image below,
       the decoding works as expected.</p>

    <pre id="received_message">Running...</pre>

    <script>
      promise_test(function() {
        var urlPath = '/common/security-features/subresource/image.py';
        var url = location.protocol + "//www1." + location.hostname + ":" + location.port +
                  urlPath + "?cache_destroyer=" + (new Date()).getTime();
        return requestViaImage(url, undefined, "always")
          .then(f