NOT FOR SUBMIT: use counters for jdm@

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 19 matching lines @@
 [
     ActiveScriptWrappable,
     DependentLifetime,
     Exposed=(Window,Worker),
 ] 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;
+    [Measure] attribute EventHandler onmessage;
 };