Expand system font values during font property parsing

Source/core/rendering/RenderTheme.h

Index: Source/core/rendering/RenderTheme.h
diff --git a/Source/core/rendering/RenderTheme.h b/Source/core/rendering/RenderTheme.h
index 8ecd33135b279ddc5e3f742703414a96925b5523..c25f2c1ed0e45ec6430ba26f0bb14ac5ee36d08b 100644
--- a/Source/core/rendering/RenderTheme.h
+++ b/Source/core/rendering/RenderTheme.h
@@ -146,7 +146,8 @@ public:
     virtual double caretBlinkInterval() const { return 0.5; }
 
     // System fonts and colors for CSS.
-    virtual void systemFont(CSSValueID, FontDescription&) const = 0;
+    virtual void systemFont(CSSValueID systemFontID, FontStyle&, FontWeight&, float& fontSize, AtomicString& fontFamily) const = 0;

[dglazkov, 2014/03/20 05:24:44]

I am curious why you cracked it open like that. Why not use FontDescription?

[alancutter (OOO until 2018), 2014/03/20 05:34:13]

Splitting the components out ensures the font style that the RenderThemes decide
upon maps cleanly to the font longhand properties, otherwise it's not clear
whether we're capturing the appropriate values off the FontDescription in the
CSSPropertyParser.

+    void systemFont(CSSValueID systemFontID, FontDescription&);
     virtual Color systemColor(CSSValueID) const;
 
     virtual int minimumMenuListSize(RenderStyle*) const { return 0; }