Less magic numbers in converting CSS lengths of cm/mm/pc/pt types.

Source/core/css/CSSHelper.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2009 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 11 matching lines @@
 #ifndef CSSHelper_h
 #define CSSHelper_h
 
 #include "wtf/Forward.h"
 
 namespace WebCore {
 
 // We always assume 96 CSS pixels in a CSS inch. This is the cold hard truth of the Web.
 // At high DPI, we may scale a CSS pixel, but the ratio of the CSS pixel to the so-called
 // "absolute" CSS length units like inch and pt is always fixed and never changes.
-const float cssPixelsPerInch = 96;
+const double cssPixelsPerInch = 96;
+const double cssPixelsPerCentimeter = cssPixelsPerInch / 2.54;

[Julien - ping for review, 2013/11/26 23:57:41]

Nit: I would put a comment with the conversion inch <-> cm for people unfamiliar
with the imperial / international system.

+const double cssPixelsPerMillimeter = cssPixelsPerCentimeter / 10;
+const double cssPixelsPerPoint = cssPixelsPerInch / 72;
+const double cssPixelsPerPica = cssPixelsPerInch / 6;
 
 } // namespace WebCore
 
 #endif // CSSHelper_h