 class="multi-line-signature">
        <span class="returntype"><a href="dart-async/ZoneCallback.html">ZoneCallback</a><span class="signature">&lt;<wbr><span class="type-parameter">R</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<