Expand system font values during property parsing.

Source/core/rendering/RenderThemeChromiumFontProvider.h

 /*
  * Copyright (C) 2012 Google Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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 #ifndef RenderThemeChromiumFontProvider_h
 #define RenderThemeChromiumFontProvider_h
 
 #include "core/CSSValueKeywords.h"
+#include "platform/fonts/FontTraits.h"
 
 namespace blink {
 
 class FontDescription;
 
 class RenderThemeChromiumFontProvider {
 public:
-    static void systemFont(CSSValueID, FontDescription&);
+    static void systemFont(CSSValueID systemFontID, FontStyle&, FontWeight&, float& fontSize, AtomicString& fontFamily);
     static void setDefaultFontSize(int);
 
 protected:
     static const WTF::AtomicString& defaultGUIFont();
 
     static float s_defaultFontSize;
 };
 
 } // namespace blink
 
 #endif // RenderThemeChromiumFontProvider_h