Have Node::document() return a reference instead of a pointer

Source/core/xml/XSLTProcessor.cpp

 /*
  * This file is part of the XSL implementation.
  *
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple, Inc. All rights reserved.
  * Copyright (C) 2005, 2006 Alexey Proskuryakov <ap@webkit.org>
  *
  * 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.
@@ skipping 42 matching lines @@
 
 XSLTProcessor::~XSLTProcessor()
 {
     // Stylesheet shouldn't outlive its root node.
     ASSERT(!m_stylesheetRootNode || !m_stylesheet || m_stylesheet->hasOneRef());
 }
 
 PassRefPtr<Document> XSLTProcessor::createDocumentFromSource(const String& sourceString,
     const String& sourceEncoding, const String& sourceMIMEType, Node* sourceNode, Frame* frame)
 {
-    RefPtr<Document> ownerDocument = sourceNode->document();
+    RefPtr<Document> ownerDocument = &sourceNode->document();
     bool sourceIsDocument = (sourceNode == ownerDocument.get());
     String documentSource = sourceString;
 
     RefPtr<Document> result;
     if (sourceMIMEType == "text/plain") {
         result = Document::create(DocumentInit(sourceIsDocument ? ownerDocument->url() : KURL(), frame));
         transformTextStringToXHTMLDocumentString(documentSource);
     } else
         result = DOMImplementation::createDocument(sourceMIMEType, frame, sourceIsDocument ? ownerDocument->url() : KURL(), false);
 
@@ skipping 71 matching lines @@
 }
 
 void XSLTProcessor::reset()
 {
     m_stylesheet.clear();
     m_stylesheetRootNode.clear();
     m_parameters.clear();
 }
 
 } // namespace WebCore