Should protect document in ProcessingInstruction::setXSLStyleSheet.

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 200 matching lines @@
 
 void ProcessingInstruction::setXSLStyleSheet(const String& href, const KURL& baseURL, const String& sheet)
 {
     if (!inDocument()) {
         ASSERT(!m_sheet);
         return;
     }
 
     ASSERT(m_isXSL);
     m_sheet = XSLStyleSheet::create(this, href, baseURL);
+    RefPtrWillBeRawPtr<Document> protect(&document());
     parseStyleSheet(sheet);
 }
 
 void ProcessingInstruction::parseStyleSheet(const String& sheet)
 {
     if (m_isCSS)
         toCSSStyleSheet(m_sheet.get())->contents()->parseString(sheet);
     else if (m_isXSL)
         toXSLStyleSheet(m_sheet.get())->parseString(sheet);
 
@@ skipping 64 matching lines @@
     m_sheet.release()->clearOwnerNode();
 }
 
 void ProcessingInstruction::trace(Visitor* visitor)
 {
     visitor->trace(m_sheet);
     CharacterData::trace(visitor);
 }
 
 } // namespace