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

Source/core/css/FontSize.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 22 matching lines @@
 
 class FontSize {
 private:
     FontSize()
     {
     }
 
 public:
     static float getComputedSizeFromSpecifiedSize(const Document*, float zoomFactor, bool isAbsoluteSize, float specifiedSize, ESmartMinimumForFontSize = UseSmartMinimumForFontFize);
 
-    // Given a CSS keyword in the range (xx-small to -webkit-xxx-large), this function will return
-    // the correct font size scaled relative to the user's default (medium).
-    static float fontSizeForKeyword(const Document*, CSSValueID keyword, FixedPitchFontType);
+    // Given a CSS keyword in the range (xx-small to -webkit-xxx-large), this function returns
+    // values from '1' to '8'.
+    static unsigned keywordSize(CSSValueID valueID)
+    {
+        ASSERT(valueID >= CSSValueXxSmall && valueID <= CSSValueWebkitXxxLarge);
+        return valueID - CSSValueXxSmall + 1;
+    }
+
+    static unsigned initialKeywordSize() { return 4; } // CSSValueMedium
+
+    // Given a keyword size in the range (1 to 8), this function will return
+    // the correct font size scaled relative to the user's default (4).
+    static float fontSizeForKeyword(const Document*, unsigned keyword, FixedPitchFontType);
 
     // Given a font size in pixel, this function will return legacy font size between 1 and 7.
     static int legacyFontSize(const Document*, int pixelFontSize, FixedPitchFontType);
 };
 
 } // namespace blink
 
 #endif // FontSize_h