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

Source/core/rendering/RenderTheme.h

 /*
  * This file is part of the theme implementation for form controls in WebCore.
  *
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 324 matching lines @@
     mutable Color m_activeSelectionBackgroundColor;
     mutable Color m_inactiveSelectionBackgroundColor;
     mutable Color m_activeSelectionForegroundColor;
     mutable Color m_inactiveSelectionForegroundColor;
 
     mutable Color m_activeListBoxSelectionBackgroundColor;
     mutable Color m_inactiveListBoxSelectionBackgroundColor;
     mutable Color m_activeListBoxSelectionForegroundColor;
     mutable Color m_inactiveListBoxSelectionForegroundColor;
 
-    mutable unsigned m_selectionColorsValid;
-
     // This color is expected to be drawn on a semi-transparent overlay,
     // making it more transparent than its alpha value indicates.
     static const RGBA32 defaultTapHighlightColor = 0x66000000;
 
 #if USE(NEW_THEME)
     Theme* m_platformTheme; // The platform-specific theme.
 #endif
 };
 
 } // namespace WebCore
 
 #endif // RenderTheme_h