V8 Microtask Queue & API

src/v8natives.js

Index: src/v8natives.js
diff --git a/src/v8natives.js b/src/v8natives.js
index df663c025e927a79222e031ab8eee14d004f67a8..e4f0a3b8600acd10e51fa09f44ad371438066806 100644
--- a/src/v8natives.js
+++ b/src/v8natives.js
@@ -1889,10 +1889,30 @@ SetUpFunction();
 // Eventually, we should move to a real event queue that allows to maintain
 // relative ordering of different kinds of tasks.
 
-RunMicrotasks.runners = new InternalArray;
+function GetMicrotaskQueue() {
+  var microtaskState = %GetMicrotaskState();
+  if (IS_UNDEFINED(microtaskState.queue)) {
+    microtaskState.queue = new InternalArray;
+  }
+  return microtaskState.queue;
+}
 
 function RunMicrotasks() {
   while (%SetMicrotaskPending(false)) {
-    for (var i in RunMicrotasks.runners) RunMicrotasks.runners[i]();
+    var microtaskState = %GetMicrotaskState();
+    if (IS_UNDEFINED(microtaskState.queue))
+      return;
+
+    var microtasks = microtaskState.queue;
+    microtaskState.queue = new InternalArray;
+
+    for (var i = 0; i < microtasks.length; i++) {
+      microtasks[i]();
+    }
   }
 }
+
+function EnqueueExternalMicrotask(fn) {
+  GetMicrotaskQueue().push(fn);
+  %SetMicrotaskPending(true);
+}