dart-async/Zone-class.html">Zone</a></span> <span class="parameter-name">zone</span>, </span><wbr><span class="parameter" id="param-f"><span class="type-annotation">R</span> <span class="parameter-name">f</span>()</span><wbr>)</span></span>
                  <span class="name ">registerCallback</span>
          
</section>
        
                        <section class="summary source-code" id="source">
          <h2><span>Implementation</span></h2>
          <pre class="language-dart"><code class="languag