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

Source/core/svg/SVGPatternElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007 Rob Buis <buis@kde.org>
  * Copyright (C) Research In Motion Limited 2010. 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.
  *
@@ skipping 199 matching lines @@
             current->patternTransformCurrentValue().concatenate(transform);
             attributes.setPatternTransform(transform);
         }
 
         if (!attributes.hasPatternContentElement() && current->childElementCount())
             attributes.setPatternContentElement(current);
 
         processedPatterns.add(current);
 
         // Respect xlink:href, take attributes from referenced element
-        Node* refNode = SVGURIReference::targetElementFromIRIString(current->hrefCurrentValue(), document());
+        Node* refNode = SVGURIReference::targetElementFromIRIString(current->hrefCurrentValue(), &document());
         if (refNode && refNode->hasTagName(SVGNames::patternTag)) {
             current = static_cast<const SVGPatternElement*>(const_cast<const Node*>(refNode));
 
             // Cycle detection
             if (processedPatterns.contains(current)) {
                 current = 0;
                 break;
             }
         } else
             current = 0;
     }
 }
 
 AffineTransform SVGPatternElement::localCoordinateSpaceTransform(SVGLocatable::CTMScope) const
 {
     AffineTransform matrix;
     patternTransformCurrentValue().concatenate(matrix);
     return matrix;
 }
 
 bool SVGPatternElement::selfHasRelativeLengths() const
 {
     return xCurrentValue().isRelative()
         || yCurrentValue().isRelative()
         || widthCurrentValue().isRelative()
         || heightCurrentValue().isRelative();
 }
 
 }