Keep auxilliary media objects on the heap always.

Source/core/html/MediaKeyError.idl

 /*
  * Copyright (C) 2012 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
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  *
  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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 [
+    GarbageCollected,
     RuntimeEnabled=PrefixedEncryptedMedia,
-    WillBeGarbageCollected,
 ] interface MediaKeyError {
     const unsigned short MEDIA_KEYERR_UNKNOWN = 1;
     const unsigned short MEDIA_KEYERR_CLIENT = 2;
     const unsigned short MEDIA_KEYERR_SERVICE = 3;
     const unsigned short MEDIA_KEYERR_OUTPUT = 4;
     const unsigned short MEDIA_KEYERR_HARDWARECHANGE = 5;
     const unsigned short MEDIA_KEYERR_DOMAIN = 6;
     readonly attribute unsigned short code;
     [RuntimeEnabled=EncryptedMedia] readonly attribute unsigned long systemCode;
 };