Simplify SVGLengthContext::valueForLength

Source/core/svg/SVGLengthContext.h

 /*
  * Copyright (C) Research In Motion Limited 2011. 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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 49 matching lines @@
         return resolveRectangle(context, type, viewport, *context->x()->currentValue(), *context->y()->currentValue(), *context->width()->currentValue(), *context->height()->currentValue());
     }
 
     static FloatRect resolveRectangle(const SVGElement*, SVGUnitTypes::SVGUnitType, const FloatRect& viewport, const SVGLength& x, const SVGLength& y, const SVGLength& width, const SVGLength& height);
     static FloatPoint resolvePoint(const SVGElement*, SVGUnitTypes::SVGUnitType, const SVGLength& x, const SVGLength& y);
     static float resolveLength(const SVGElement*, SVGUnitTypes::SVGUnitType, const SVGLength&);
 
     float convertValueToUserUnits(float, SVGLengthMode, SVGLengthType fromUnit) const;
     float convertValueFromUserUnits(float, SVGLengthMode, SVGLengthType toUnit) const;
 
-    float valueForLength(const Length&, SVGLengthMode = LengthModeOther);
+    float valueForLength(const Length&, SVGLengthMode = LengthModeOther) const;
 
     bool determineViewport(FloatSize&) const;
 
 private:
     float convertValueFromUserUnitsToEMS(float value) const;
     float convertValueFromEMSToUserUnits(float value) const;
 
     float convertValueFromUserUnitsToEXS(float value) const;
     float convertValueFromEXSToUserUnits(float value) const;
 
     RawPtrWillBeMember<const SVGElement> m_context;
 };
 
 } // namespace blink
 
 #endif // SVGLengthContext_h