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

Source/core/svg/SVGFitToViewBox.h

 /*
  * Copyright (C) 2004, 2005, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2010 Rob Buis <buis@kde.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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 25 matching lines @@
 public:
     static AffineTransform viewBoxToViewTransform(const FloatRect& viewBoxRect, const SVGPreserveAspectRatio&, float viewWidth, float viewHeight);
 
     static bool isKnownAttribute(const QualifiedName&);
     static void addSupportedAttributes(HashSet<QualifiedName>&);
 
     template<class SVGElementTarget>
     static bool parseAttribute(SVGElementTarget* target, const QualifiedName& name, const AtomicString& value)
     {
         ASSERT(target);
-        ASSERT(target->document());
         if (name == SVGNames::viewBoxAttr) {
             FloatRect viewBox;
-            bool valueIsValid = !value.isNull() && parseViewBox(target->document(), value, viewBox);
+            bool valueIsValid = !value.isNull() && parseViewBox(&target->document(), value, viewBox);
             target->setViewBoxBaseValue(viewBox, valueIsValid);
             return true;
         }
 
         if (name == SVGNames::preserveAspectRatioAttr) {
             SVGPreserveAspectRatio preserveAspectRatio;
             preserveAspectRatio.parse(value);
             target->setPreserveAspectRatioBaseValue(preserveAspectRatio);
             return true;
         }
 
         return false;
     }
 
     static bool parseViewBox(Document*, const LChar*& start, const LChar* end, FloatRect& viewBox, bool validate = true);
     static bool parseViewBox(Document*, const UChar*& start, const UChar* end, FloatRect& viewBox, bool validate = true);
 
 private:
     static bool parseViewBox(Document*, const String&, FloatRect&);
 };
 
 } // namespace WebCore
 
 #endif // SVGFitToViewBox_h