Move isValid/isCurrentColor from Color to StyleColor

Source/core/rendering/style/StyleBackgroundData.h

Index: Source/core/rendering/style/StyleBackgroundData.h
diff --git a/Source/core/rendering/style/StyleBackgroundData.h b/Source/core/rendering/style/StyleBackgroundData.h
index d2d834aeda4203c320a4f9adecda2b902ac80001..6c58b0217cd672d5fa1869ba5b63d56c142f2d91 100644
--- a/Source/core/rendering/style/StyleBackgroundData.h
+++ b/Source/core/rendering/style/StyleBackgroundData.h
@@ -25,7 +25,7 @@
 #ifndef StyleBackgroundData_h
 #define StyleBackgroundData_h
 
-#include "core/platform/graphics/Color.h"
+#include "core/css/StyleColor.h"
 #include "core/rendering/style/FillLayer.h"
 #include "core/rendering/style/OutlineValue.h"
 #include <wtf/PassRefPtr.h>
@@ -46,7 +46,7 @@ public:
     }
 
     const FillLayer& background() const { return m_background; }
-    const Color& color() const { return m_color; }
+    const StyleColor& color() const { return m_color; }
     const OutlineValue& outline() const { return m_outline; }
 
 private:
@@ -56,7 +56,7 @@ private:
     StyleBackgroundData(const StyleBackgroundData&); 
 
     FillLayer m_background;
-    Color m_color;
+    StyleColor m_color;
     OutlineValue m_outline;
 };