Have ProcessingInstruction's XSLT event listener keep a weak backreference

Source/core/dom/ProcessingInstruction.cpp

 /*
  * Copyright (C) 2000 Peter Kelly (pmk@post.com)
  * Copyright (C) 2006, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 49 matching lines @@
 #if !ENABLE(OILPAN)
     if (m_sheet)
         clearSheet();
 
     // FIXME: ProcessingInstruction should not be in document here.
     // However, if we add ASSERT(!inDocument()), fast/xsl/xslt-entity.xml
     // crashes. We need to investigate ProcessingInstruction lifetime.
     if (inDocument() && m_isCSS)
         document().styleEngine()->removeStyleSheetCandidateNode(this);
 #endif
+    clearEventListenerForXSLT();
+}
+
+EventListener* ProcessingInstruction::eventListenerForXSLT()
+{
+    if (!m_listenerForXSLT)
+        return 0;
+
+    return m_listenerForXSLT->toEventListener();
+}
+
+void ProcessingInstruction::clearEventListenerForXSLT()
+{
+    if (m_listenerForXSLT) {
+        m_listenerForXSLT->detach();
+        m_listenerForXSLT.clear();
+    }
 }
 
 String ProcessingInstruction::nodeName() const
 {
     return m_target;
 }
 
 Node::NodeType ProcessingInstruction::nodeType() const
 {
     return PROCESSING_INSTRUCTION_NODE;
@@ skipping 220 matching lines @@
     m_sheet.release()->clearOwnerNode();
 }
 
 void ProcessingInstruction::trace(Visitor* visitor)
 {
     visitor->trace(m_sheet);
     CharacterData::trace(visitor);
 }
 
 } // namespace