V8 Microtask Queue & API

src/v8natives.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1888 matching lines @@
 // relative ordering of different kinds of tasks.
 
 RunMicrotasks.queue = new InternalArray;
 
 function RunMicrotasks() {
   while (%SetMicrotaskPending(false)) {
     var microtasks = RunMicrotasks.queue;
     RunMicrotasks.queue = new InternalArray;
 
     for (var i = 0; i < microtasks.length; i++) {
-      microtasks[i]();
+      var microtask = microtasks[i];
+      if (typeof microtask === 'function')
+        microtask();
+      else
+        %RunExternalMicrotask(microtask);
     }
   }
 }
+
+function EnqueueExternalMicrotask(handler) {
+  %SetMicrotaskPending(true);
+  RunMicrotasks.queue.push(handler);
+}