Oilpan: have PendingScripts trace their script elements.

Source/core/dom/PendingScript.cpp

 /*
  * Copyright (C) 2010 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 17 matching lines @@
 
 #include "core/dom/Element.h"
 #include "core/fetch/ScriptResource.h"
 
 namespace WebCore {
 
 PendingScript::~PendingScript()
 {
 }
 
-PassRefPtr<Element> PendingScript::releaseElementAndClear()
+PassRefPtrWillBeRawPtr<Element> PendingScript::releaseElementAndClear()
 {
     setScriptResource(0);
     m_watchingForLoad = false;
     m_startingPosition = TextPosition::belowRangePosition();
     return m_element.release();
 }
 
 void PendingScript::setScriptResource(ScriptResource* resource)
 {
     setResource(resource);
 }
 
 void PendingScript::notifyFinished(Resource*)
 {
 }
 
+void PendingScript::trace(Visitor* visitor)
+{
+    // FIXME: Oilpan: this trace() is for a PendingScript that's not
+    // on the heap -- it is kept by script runner objects
+    // (ScriptRunner and HTMLScriptRunner), which are OwnPtr-kept by
+    // the document and the HTML document parser, respectively. The
+    // reason they are OwnPtrs and not on the heap themselves, is due
+    // to their need to finalize by using their hosts -- something
+    // that's not readily doable if both host and script runner object
+    // are heap allocated.
+    //
+    // Find a better arrangment, or at least clarify that this is the
+    // most practical way to handle such a dependency.
+    visitor->trace(m_element);
 }
+
+}