Move isValid/isCurrentColor from Color to StyleColor

Source/web/mac/WebSubstringUtil.mm

 /*
  * Copyright (C) 2005, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Google 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:
  * 
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 73 matching lines @@
         NSFont* font = style->font().primaryFont()->getNSFont();
         // If the platform font can't be loaded, it's likely that the site is
         // using a web font. For now, just use the default font instead.
         // TODO(rsesek): Change the font activation flags to allow other processes
         // to use the font.
         if (!font)
           font = [NSFont systemFontOfSize:style->font().size()];
         [attrs setObject:font forKey:NSFontAttributeName];
 
         if (style->visitedDependentColor(CSSPropertyColor).alpha())
-            [attrs setObject:nsColor(style->visitedDependentColor(CSSPropertyColor)) forKey:NSForegroundColorAttributeName];
+            [attrs setObject:nsColor(renderer->resolveColor(CSSPropertyColor)) forKey:NSForegroundColorAttributeName];
         else
             [attrs removeObjectForKey:NSForegroundColorAttributeName];
         if (style->visitedDependentColor(CSSPropertyBackgroundColor).alpha())
-            [attrs setObject:nsColor(style->visitedDependentColor(CSSPropertyBackgroundColor)) forKey:NSBackgroundColorAttributeName];
+            [attrs setObject:nsColor(renderer->resolveColor(CSSPropertyBackgroundColor)) forKey:NSBackgroundColorAttributeName];
         else
             [attrs removeObjectForKey:NSBackgroundColorAttributeName];
 
         Vector<UChar> characters;
         it.appendTextTo(characters);
         NSString* substring =
             [[[NSString alloc] initWithCharacters:characters.data()
                                            length:characters.size()] autorelease];
         [string replaceCharactersInRange:NSMakeRange(position, 0)
                               withString:substring];
         [string setAttributes:attrs range:NSMakeRange(position, numCharacters)];
         position += numCharacters;
     }
     return [string autorelease];
 }
 
 } // namespace WebKit