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

Source/platform/graphics/Color.h

Index: Source/platform/graphics/Color.h
diff --git a/Source/platform/graphics/Color.h b/Source/platform/graphics/Color.h
index ce371ab23f8059206463c0de934ed0595f03c0aa..05d7588ae22ca3f365cfc14f574bd7e5c2f256a8 100644
--- a/Source/platform/graphics/Color.h
+++ b/Source/platform/graphics/Color.h
@@ -122,6 +122,10 @@ public:
     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&);