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

Source/core/rendering/svg/SVGRenderingContext.cpp

 /*
  * Copyright (C) 2007, 2008 Rob Buis <buis@kde.org>
  * Copyright (C) 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2007 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Google, Inc.  All rights reserved.
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  * Copyright (C) Research In Motion Limited 2009-2010. 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
@@ skipping 190 matching lines @@
     calculateTransformationToOutermostCoordinateSystem(renderer, ctm);
     return narrowPrecisionToFloat(sqrt((pow(ctm.xScale(), 2) + pow(ctm.yScale(), 2)) / 2));
 }
 
 void SVGRenderingContext::calculateTransformationToOutermostCoordinateSystem(const RenderObject* renderer, AffineTransform& absoluteTransform)
 {
     ASSERT(renderer);
     absoluteTransform = currentContentTransformation();
 
     float deviceScaleFactor = 1;
-    ASSERT(renderer->document());
-    if (Page* page = renderer->document()->page())
+    if (Page* page = renderer->document().page())
         deviceScaleFactor = page->deviceScaleFactor();
 
     // Walk up the render tree, accumulating SVG transforms.
     while (renderer) {
         absoluteTransform = renderer->localToParentTransform() * absoluteTransform;
         if (renderer->isSVGRoot())
             break;
         renderer = renderer->parent();
     }
 
@@ skipping 123 matching lines @@
             toRenderSVGImage(m_object)->paintForeground(bufferedInfo);
         } else
             return false;
     }
 
     m_paintInfo->context->drawImageBuffer(imageBuffer.get(), boundingBox);
     return true;
 }
 
 }