Add use counters to determine the fate of DOMError

Source/modules/indexeddb/IDBTransaction.idl

  /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2011 Apple 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.
@@ skipping 26 matching lines @@
 [
     Exposed=(Window,Worker),
     ActiveDOMObject,
     GarbageCollected
 ] interface IDBTransaction : EventTarget {
 
     // Properties
     [RuntimeEnabled=IndexedDBExperimental] readonly attribute DOMStringList objectStoreNames;
     readonly attribute IDBTransactionMode mode;
     readonly attribute IDBDatabase db;
-    readonly attribute DOMError error;
+    [Measure] readonly attribute DOMError error;
 
     // Methods
     [RaisesException] IDBObjectStore objectStore (DOMString name);
     [RaisesException] void abort ();
 
     // Events
     attribute EventHandler onabort;
     attribute EventHandler oncomplete;
     attribute EventHandler onerror;
 };