Add support for converting Colors to linear RGB; Fix relevant filters

Source/platform/graphics/Color.h

 /*
  * Copyright (C) 2003, 2004, 2005, 2006, 2010 Apple 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
@@ skipping 104 matching lines @@
 
     Color light() const;
     Color dark() const;
 
     Color combineWithAlpha(float otherAlpha) const;
 
     // This is an implementation of Porter-Duff's "source-over" equation
     Color blend(const Color&) const;
     Color blendWithWhite() const;
 
+    // Convert a Color assumed to be in the device RGB space into a Color in
+    // linear RGB space.
+    Color convertToLinear() const;

[f(malita), 2014/01/22 15:09:32]

This is just a bit odd - Color feels too low-level for color space assumptions.

I think at this level we should have a generic convertToColorSpace(ColorSpace),
and relocate the assumption to FilterEffect::adaptColorToOperatingColorSpace().

Or maybe there's a better home for the color space conversion method (ColorSpace
class? see below)...

+
     static bool parseHexColor(const String&, RGBA32&);
     static bool parseHexColor(const LChar*, unsigned, RGBA32&);
     static bool parseHexColor(const UChar*, unsigned, RGBA32&);
 
     static const RGBA32 black = 0xFF000000;
     static const RGBA32 white = 0xFFFFFFFF;
     static const RGBA32 darkGray = 0xFF808080;
     static const RGBA32 gray = 0xFFA0A0A0;
     static const RGBA32 lightGray = 0xFFC0C0C0;
     static const RGBA32 transparent = 0x00000000;
@@ skipping 32 matching lines @@
     }
 
     return Color(blend(from.red(), to.red(), progress),
                  blend(from.green(), to.green(), progress),
                  blend(from.blue(), to.blue(), progress),
                  blend(from.alpha(), to.alpha(), progress));
 }
 } // namespace WebCore
 
 #endif // Color_h