Fix |RunMicrotasks()| leaking reference to the last context being run on.

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 1875 matching lines @@
 
 SetUpFunction();
 
 
 //----------------------------------------------------------------------------
 
 // TODO(rossberg): very simple abstraction for generic microtask queue.
 // Eventually, we should move to a real event queue that allows to maintain
 // relative ordering of different kinds of tasks.
 
-function GetMicrotaskQueue() {
-  var microtaskState = %GetMicrotaskState();
-  if (IS_UNDEFINED(microtaskState.queue)) {
-    microtaskState.queue = new InternalArray;
-  }
-  return microtaskState.queue;
-}
-
 function RunMicrotasks() {
   while (%SetMicrotaskPending(false)) {
     var microtaskState = %GetMicrotaskState();
     if (IS_UNDEFINED(microtaskState.queue))
       return;
 
     var microtasks = microtaskState.queue;
-    microtaskState.queue = new InternalArray;
+    microtaskState.queue = null;
 
     for (var i = 0; i < microtasks.length; i++) {
       microtasks[i]();
     }
   }
 }
 
-function EnqueueExternalMicrotask(fn) {
-  GetMicrotaskQueue().push(fn);
+function EnqueueMicrotask(fn) {
+  var microtaskState = %GetMicrotaskState();
+  if (IS_UNDEFINED(microtaskState.queue) || IS_NULL(microtaskState.queue)) {
+    microtaskState.queue = new InternalArray;
+  }
+  microtaskState.queue.push(fn);
   %SetMicrotaskPending(true);
 }