Don't repaint when setting border or outline 0 with style none

Source/core/rendering/style/BorderValue.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *
  * 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
@@ skipping 45 matching lines @@
     bool isVisible(bool checkStyle = true) const
     {
         return nonZero(checkStyle) && !isTransparent() && (!checkStyle || m_style != BHIDDEN);
     }
 
     bool operator==(const BorderValue& o) const
     {
         return m_width == o.m_width && m_style == o.m_style && m_color == o.m_color && m_colorIsCurrentColor == o.m_colorIsCurrentColor;
     }
 
+    // The default width is 3px, but if the style is none we compute a value of 0 (in RenderStyle itself)
+    bool visuallyEqual(const BorderValue& o) const
+    {
+        if (m_style == BNONE && o.m_style == BNONE)
+            return true;
+        if (m_style == BHIDDEN && o.m_style == BHIDDEN)
+            return true;
+        return *this == o;
+    }
+
     bool operator!=(const BorderValue& o) const
     {
         return !(*this == o);
     }
 
     void setColor(const StyleColor& color)
     {
         m_color = color.resolve(Color());
         m_colorIsCurrentColor = color.isCurrentColor();
     }
@@ skipping 10 matching lines @@
     unsigned m_width : 26;
     unsigned m_style : 4; // EBorderStyle
 
     // This is only used by OutlineValue but moved here to keep the bits packed.
     unsigned m_isAuto : 1; // OutlineIsAuto
 };
 
 } // namespace WebCore
 
 #endif // BorderValue_h