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

Source/core/rendering/svg/SVGInlineFlowBox.cpp

 /*
  * Copyright (C) 2006 Oliver Hunt <ojh16@student.canterbury.ac.nz>
  * Copyright (C) 2006 Apple Computer Inc.
  * Copyright (C) 2007 Nikolas Zimmermann <zimmermann@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 71 matching lines @@
     ASSERT(textRenderer);
 
     Node* node = textRenderer->node();
     if (!node || !node->inDocument())
         return;
 
     RenderStyle* style = textRenderer->style();
     ASSERT(style);
 
     AffineTransform fragmentTransform;
-    Document* document = textRenderer->document();
-    Vector<DocumentMarker*> markers = document->markers()->markersFor(textRenderer->node());
+    Document& document = textRenderer->document();
+    Vector<DocumentMarker*> markers = document.markers()->markersFor(textRenderer->node());
 
     Vector<DocumentMarker*>::iterator markerEnd = markers.end();
     for (Vector<DocumentMarker*>::iterator markerIt = markers.begin(); markerIt != markerEnd; ++markerIt) {
         DocumentMarker* marker = *markerIt;
 
         // SVG is only interessted in the TextMatch marker, for now.
         if (marker->type() != DocumentMarker::TextMatch)
             continue;
 
         FloatRect markerRect;
@@ skipping 29 matching lines @@
 
                 markerRect.unite(fragmentRect);
             }
         }
 
         toRenderedDocumentMarker(marker)->setRenderedRect(textRenderer->localToAbsoluteQuad(markerRect).enclosingBoundingBox());
     }
 }
 
 } // namespace WebCore