Revert r154797: "Move isValid/isCurrentColor from Color to StyleColor"

Source/core/rendering/style/StyleMultiColData.h

Index: Source/core/rendering/style/StyleMultiColData.h
diff --git a/Source/core/rendering/style/StyleMultiColData.h b/Source/core/rendering/style/StyleMultiColData.h
index bc971845daa341f20b9983ed0dd34bd4d3da4306..dcd1478ca8d8b3232fe3183281b51e51bc113b46 100644
--- a/Source/core/rendering/style/StyleMultiColData.h
+++ b/Source/core/rendering/style/StyleMultiColData.h
@@ -25,7 +25,6 @@
 #ifndef StyleMultiColData_h
 #define StyleMultiColData_h
 
-#include "core/css/StyleColor.h"
 #include "core/platform/Length.h"
 #include "core/rendering/style/BorderValue.h"
 #include "core/rendering/style/RenderStyleConstants.h"
@@ -58,7 +57,7 @@ public:
     unsigned short m_count;
     float m_gap;
     BorderValue m_rule;
-    StyleColor m_visitedLinkColumnRuleColor;
+    Color m_visitedLinkColumnRuleColor;
 
     bool m_autoWidth : 1;
     bool m_autoCount : 1;