Oilpan: have History on the heap by default.

Source/core/frame/History.idl

 /*
  * Copyright (C) 2007, 2008 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.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * 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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  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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 [
-    WillBeGarbageCollected,
+    GarbageCollected,
 ] interface History {
     readonly attribute unsigned long length;
     [CachedAttribute=stateChanged] readonly attribute SerializedScriptValue state;
 
     [CallWith=ExecutionContext] void back();
     [CallWith=ExecutionContext] void forward();
     [CallWith=ExecutionContext] void go([Default=Undefined] optional long distance);
 
     // FIXME: the title arguments below should simply be 'DOMString title'.
     [RaisesException] void pushState(SerializedScriptValue data, [TreatUndefinedAs=NullString] DOMString? title, optional DOMString? url = null);
     [RaisesException] void replaceState(SerializedScriptValue data, [TreatUndefinedAs=NullString] DOMString? title, optional DOMString? url = null);
 };