Make style building for 'font-size' less custom.

Source/platform/fonts/FontDescription.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  *
  * 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
@@ skipping 85 matching lines @@
             , contextual(NormalLigaturesState)
         {
         }
 
         unsigned common : 2;
         unsigned discretionary : 2;
         unsigned historical : 2;
         unsigned contextual : 2;
     };
 
+    struct Size {
+        Size(unsigned keyword, float value, bool isAbsolute)
+            : keyword(keyword)
+            , isAbsolute(isAbsolute)
+            , value(value)
+        {
+        }
+        unsigned keyword : 4; // FontDescription::keywordSize
+        unsigned isAbsolute : 1; // FontDescription::isAbsoluteSize
+        float value;
+    };
+
     const FontFamily& family() const { return m_familyList; }
     FontFamily& firstFamily() { return m_familyList; }
+    Size size() const { return Size(m_keywordSize, m_specifiedSize, m_isAbsoluteSize); }
     float specifiedSize() const { return m_specifiedSize; }
     float computedSize() const { return m_computedSize; }
     FontStyle style() const { return static_cast<FontStyle>(m_style); }
     int computedPixelSize() const { return int(m_computedSize + 0.5f); }
     FontVariant variant() const { return static_cast<FontVariant>(m_variant); }
     bool isAbsoluteSize() const { return m_isAbsoluteSize; }
     FontWeight weight() const { return static_cast<FontWeight>(m_weight); }
     FontStretch stretch() const { return static_cast<FontStretch>(m_stretch); }
     static FontWeight lighterWeight(FontWeight);
     static FontWeight bolderWeight(FontWeight);
+    static Size largerSize(const Size&);
+    static Size smallerSize(const Size&);
     GenericFamilyType genericFamily() const { return static_cast<GenericFamilyType>(m_genericFamily); }
 
     // only use fixed default size when there is only one font family, and that family is "monospace"
     FixedPitchFontType fixedPitchFontType() const
     {
         if (genericFamily() == MonospaceFamily && !family().next() && family().family() == FontFamilyNames::webkit_monospace)
             return FixedPitchFont;
         return NonFixedPitchFont;
     }
     Kerning kerning() const { return static_cast<Kerning>(m_kerning); }
@@ skipping 135 matching lines @@
         && m_script == other.m_script
         && m_syntheticBold == other.m_syntheticBold
         && m_syntheticItalic == other.m_syntheticItalic
         && m_featureSettings == other.m_featureSettings
         && m_subpixelTextPosition == other.m_subpixelTextPosition;
 }
 
 } // namespace blink
 
 #endif