span>&gt;</span></span>
                <span class="name ">RegisterCallbackHandler</span>
&lt;<wbr><span class="type-parameter">R</span>&gt;(<wbr><span class="parameter" id="RegisterCallbackHandler-param-self"><span class="type-annotation"><a href="dart-async/Zone-class.html">Zone</a></span> <span class="parameter-name">self</span>, </span> <span class="parameter" id="RegisterCallbackHandler-param-parent"><span class="type-annotation"><a href="dart-async/ZoneDelegate-class.html">ZoneDelegate</a></span> <sp