Fix when fast/events/message-port-gc-closed.html forces a GC.

LayoutTests/fast/events/message-port-gc-closed.html

Index: LayoutTests/fast/events/message-port-gc-closed.html
diff --git a/LayoutTests/fast/events/message-port-gc-closed.html b/LayoutTests/fast/events/message-port-gc-closed.html
index 0be397f62a154a78942ab169725bd02f38ad1935..4cc906ac01e6d48f7137bbe1ba35e4e19ad4ad8b 100644
--- a/LayoutTests/fast/events/message-port-gc-closed.html
+++ b/LayoutTests/fast/events/message-port-gc-closed.html
@@ -5,18 +5,21 @@
 description("MessagePorts (and their execution contexts) should be collected by GC once close() has been called on them");
 
 window.jsTestIsAsync = true;
+
+function runGCAndTest() {
+    gc();
+    shouldBeTrue("iframeDocGC.wasCollected");
+    finishJSTest();
+}
+
 window.onmessage = function(evt) {
     iframeDocGC = internals.observeGC(document.querySelector('iframe').contentDocument);
     document.querySelector('iframe').remove();
     // The iframe is reachable via evt.source, and evt is on the
-    // stack. asyncGC() will invoke the callback once back at
-    // the event loop (and after having forced a GC); evt
-    // will consequently no longer be in scope and the iframe
-    // will have been GCed.
-    asyncGC(function () {
-        shouldBeTrue("iframeDocGC.wasCollected");
-        finishJSTest();
-    });
+    // stack. Force a GC upon return from the event handler, so
+    // that it no longer will be in scope and the iframe can
+    // be GCed.
+    setTimeout(runGCAndTest, 0);
 }
 </script>
 <iframe src="resources/message-port-gc-closed-iframe.html"></iframe>