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

Source/web/mac/WebSubstringUtil.mm

Index: Source/web/mac/WebSubstringUtil.mm
diff --git a/Source/web/mac/WebSubstringUtil.mm b/Source/web/mac/WebSubstringUtil.mm
index 055981e0870104ee049022f885dd0a471edfdb31..9f6a1b39e8420fea95683d834a8e6da035089386 100644
--- a/Source/web/mac/WebSubstringUtil.mm
+++ b/Source/web/mac/WebSubstringUtil.mm
@@ -91,11 +91,11 @@ NSAttributedString* WebSubstringUtil::attributedSubstringInRange(WebFrame* webFr
         [attrs setObject:font forKey:NSFontAttributeName];
 
         if (style->visitedDependentColor(CSSPropertyColor).alpha())
-            [attrs setObject:nsColor(renderer->resolveColor(CSSPropertyColor)) forKey:NSForegroundColorAttributeName];
+            [attrs setObject:nsColor(style->visitedDependentColor(CSSPropertyColor)) forKey:NSForegroundColorAttributeName];
         else
             [attrs removeObjectForKey:NSForegroundColorAttributeName];
         if (style->visitedDependentColor(CSSPropertyBackgroundColor).alpha())
-            [attrs setObject:nsColor(renderer->resolveColor(CSSPropertyBackgroundColor)) forKey:NSBackgroundColorAttributeName];
+            [attrs setObject:nsColor(style->visitedDependentColor(CSSPropertyBackgroundColor)) forKey:NSBackgroundColorAttributeName];
         else
             [attrs removeObjectForKey:NSBackgroundColorAttributeName];