Expose MessagePort to AudioWorklet

See WebAudio/web-audio-api#1266 for details.

Test plan: WebAudio/web-audio-api#1388.

Fixes whatwg#3081.

Author: hoch

source

@@ -93125,7 +93125,7 @@ loadMySprites().then(runDemo);</pre>
   <code>MessageEvent</code> interface for their <code data-x="event-message">message</code>
   events:</p>
 
-  <pre class="idl">[Constructor(DOMString type, optional <span>MessageEventInit</span> eventInitDict), Exposed=(Window,Worker)]
+  <pre class="idl">[Constructor(DOMString type, optional <span>MessageEventInit</span> eventInitDict), Exposed=(Window,Worker,AudioWorklet)]
 interface <dfn>MessageEvent</dfn> : <span>Event</span> {
   readonly attribute any <span data-x="dom-MessageEvent-data">data</span>;
   readonly attribute USVString <span data-x="dom-MessageEvent-origin">origin</span>;
@@ -95301,7 +95301,7 @@ interface <dfn>MessageChannel</dfn> {
   <p>Each channel has two message ports. Data sent through one port is received by the other port,
   and vice versa.</p>
 
-  <pre class="idl">[Exposed=(Window,Worker), <span>Transferable</span>]
+  <pre class="idl">[Exposed=(Window,Worker,AudioWorklet), <span>Transferable</span>]
 interface <dfn>MessagePort</dfn> : <span>EventTarget</span> {
   void <span data-x="dom-MessagePort-postMessage">postMessage</span>(any message, optional sequence&lt;<span data-x="idl-object">object</span>&gt; transfer = []);
   void <span data-x="dom-MessagePort-start">start</span>();
@@ -120253,6 +120253,7 @@ INSERT INTERFACES HERE
   Henry Story,
   Hermann Donfack Zeufack,
   Hiroshige Hayashizaki,
+  Hongchan Choi, <!-- hoch on GitHub -->
   Hugh Bellamy,
   Hugh Guiney,
   Hugh Winkler,