an class="parameter-name">header</span></span>)
                      &#8594;
                      <span class="returntype">String</span>
                  </span>
              </dt>
              <dd>
                  Return the response header named <code class="prettyprint lang-dart">header</code>, or null if not found.
              </dd>
              <dt id="open" class="callable">
                  <a href="polymer_app_layout/HttpRequest/open.html"><span class="name ">open</span></a><span class="s