Less magic numbers in converting CSS lengths of cm/mm/pc/pt types.

Source/core/svg/SVGSVGElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010 Rob Buis <buis@kde.org>
  * Copyright (C) 2007 Apple Inc. 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 127 matching lines @@
 
 SVGRect SVGSVGElement::viewport() const
 {
     // FIXME: This method doesn't follow the spec and is basically untested. Parent documents are not considered here.
     // As we have no test coverage for this, we're going to disable it completly for now.
     return SVGRect();
 }
 
 float SVGSVGElement::pixelUnitToMillimeterX() const
 {
-    // 2.54 / cssPixelsPerInch gives CM.
-    return (2.54f / cssPixelsPerInch) * 10.0f;
+    return 1 / cssPixelsPerMillimeter;
 }
 
 float SVGSVGElement::pixelUnitToMillimeterY() const
 {
-    // 2.54 / cssPixelsPerInch gives CM.
-    return (2.54f / cssPixelsPerInch) * 10.0f;
+    return 1 / cssPixelsPerMillimeter;
 }
 
 float SVGSVGElement::screenPixelToMillimeterX() const
 {
     return pixelUnitToMillimeterX();
 }
 
 float SVGSVGElement::screenPixelToMillimeterY() const
 {
     return pixelUnitToMillimeterY();
@@ skipping 609 matching lines @@
             continue;
 
         Element* element = toElement(node);
         if (element->getIdAttribute() == id)
             return element;
     }
     return 0;
 }
 
 }