[WIP] Add Atomics.waitAsync host hook

This host hook queues a task in the appropriate agent to resolve a Promise.

Corresponding PR: tc39/proposal-atomics-wait-async#7

source

@@ -3116,6 +3116,14 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
 
     <p>User agents that support JavaScript must also implement the <cite>BigInt</cite> proposal. <ref
     spec=JSBIGINT></p>
+
+    <p>User agents that support JavaScript must also implement the <cite>Atomics.waitAsync</cite>
+    proposal. The following term is defined there, and used in this specification: <ref
+    spec=JSWAITASYNC></p>
+
+    <ul class="brief">
+     <li>The <dfn data-x="js-HostResolveInAgent" data-x-href="https://tc39.github.io/proposal-atomics-wait-async/#sec-hostresolveinagent">HostResolveInAgent</dfn> abstract operation</li>
+    </ul>
    </dd>
 
 
@@ -89465,6 +89473,22 @@ dictionary <dfn>PromiseRejectionEventInit</dfn> : <span>EventInit</span> {
 
   </ol>
 
+  <h5><dfn data-x="the-hostresolveinagent-implementation">HostResolveInAgent</dfn>(<var>agentSignifier</var>, <var>promiseCapability</var>, <var>resolution</var>)</h5>
+
+  <p>The <cite>Atomics.waitAsync</cite> specification relies on the host to trigger the resolution of a <code data-x="">Promise</code> in another <span>agent</span>. This specification defines that algorithm as follows: <ref spec=JSWAITASYNC></p>
+
+  <ol>
+   <li><p>Let <var>agent</var> be the <span>agent</span> corresponding to <var>agentSignifier</var>.</p></li>
+   <li>
+    <p><span>Queue a task</span> on the <span>Atomics.waitAsync task source</span> in <var>agent</var>'s <span>event loop</span> to run the following steps:</p>
+    <ol>
+     <li>Perform ! <span>Call</span>(<var>promiseCapability</var>.[[Resolve]], undefined, &laquo; <var>resolution</var> &raquo;).</li>
+    </ol>
+   </li>
+  </ol>
+
+  <p>The <span>task source</span> for these <span data-x="concept-task">tasks</span> in this section is the <dfn>Atomics.waitAsync task source</dfn>.</p>
+
   </div>
 
   <h4>Event loops</h4> <!-- <dfn>event loop</dfn> -->
@@ -121967,6 +121991,9 @@ INSERT INTERFACES HERE
    <dt id="refsJSON">[JSON]</dt>
    <dd><cite><a href="https://tools.ietf.org/html/rfc7159">The JavaScript Object Notation (JSON) Data Interchange Format</a></cite>, T. Bray. IETF.</dd>
 
+   <dt id="refsJSWAITASYNC">[JSWAITASYNC]</dt>
+   <dd><cite><a href="https://tc39.github.io/proposal-atomics-wait-async/">Atomics.waitAsync</a></cite>. Ecma International.</dd>
+
    <dt id="refsLONGTASKS">[LONGTASKS]</dt>
    <dd><cite><a href="https://w3c.github.io/longtasks/">Long Tasks</a></cite>, D. Denicola, I. Grigorik, S. Panicker. W3C.</dd>