e-annotation">String</span> <span class="parameter-name">responseType</span></span>, <span class="parameter" id="postFormData-param-requestHeaders"><span class="type-annotation">Map&lt;String,String&gt;</span> <span class="parameter-name">requestHeaders</span></span>, <span class="parameter" id="postFormData-param-onProgress"><span class="type-annotation">void</span> <span class="parameter-name">onProgress</span>(<span class="parameter" id="onProgress-param-e"><span class="type-annotation"><a href="polymer_