[v8 gc] Introduce a base class for all objects that can have pending activity

third_party/WebKit/Source/core/dom/MessagePort.idl

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2011 Google Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 10 matching lines @@
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  */
 
 // https://html.spec.whatwg.org/#message-ports
 
 [
+    ActiveScriptWrappable,
     DependentLifetime,
     Exposed=(Window,Worker),
     GarbageCollected,
 ] interface MessagePort : EventTarget {
     [PostMessage, RaisesException, Measure] void postMessage(any message, optional sequence<Transferable> transfer);
     [Measure] void start();
     [Measure] void close();
 
     // event handlers
     attribute EventHandler onmessage;
 };