Factor painting code out of RenderBox into a new class called BoxPainter.

Source/core/rendering/style/RenderStyle.cpp

 /*
  * Copyright (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Adobe Systems Incorporated. All rights reserved.
  *
  * 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 10 matching lines @@
  */
 
 #include "config.h"
 #include "core/rendering/style/RenderStyle.h"
 
 #include <algorithm>
 #include "core/css/resolver/StyleResolver.h"
 #include "core/rendering/RenderTheme.h"
 #include "core/rendering/TextAutosizer.h"
 #include "core/rendering/style/AppliedTextDecoration.h"
+#include "core/rendering/style/BorderEdge.h"
 #include "core/rendering/style/ContentData.h"
 #include "core/rendering/style/DataEquivalency.h"
 #include "core/rendering/style/QuotesData.h"
 #include "core/rendering/style/ShadowList.h"
 #include "core/rendering/style/StyleImage.h"
 #include "core/rendering/style/StyleInheritedData.h"
 #include "platform/LengthFunctions.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/fonts/Font.h"
 #include "platform/fonts/FontSelector.h"
@@ skipping 1647 matching lines @@
 
     // right
     radiiSum = radii.topRight().height() + radii.bottomRight().height();
     if (radiiSum > rect.height())
         factor = std::min(rect.height() / radiiSum, factor);
 
     ASSERT(factor <= 1);
     return factor;
 }
 
+bool RenderStyle::borderObscuresBackground() const
+{
+    if (!hasBorder())
+        return false;
+
+    // Bail if we have any border-image for now. We could look at the image alpha to improve this.
+    if (borderImage().image())
+        return false;
+
+    BorderEdge edges[4];
+    getBorderEdgeInfo(edges);
+
+    for (int i = BSTop; i <= BSLeft; ++i) {
+        const BorderEdge& currEdge = edges[i];
+        if (!currEdge.obscuresBackground())
+            return false;
+    }
+
+    return true;
+}
+
+void RenderStyle::getBorderEdgeInfo(BorderEdge edges[], bool includeLogicalLeftEdge, bool includeLogicalRightEdge) const
+{
+    bool horizontal = isHorizontalWritingMode();
+
+    edges[BSTop] = BorderEdge(borderTopWidth(),
+        visitedDependentColor(CSSPropertyBorderTopColor),
+        borderTopStyle(),
+        borderTopIsTransparent(),
+        horizontal || includeLogicalLeftEdge);
+
+    edges[BSRight] = BorderEdge(borderRightWidth(),
+        visitedDependentColor(CSSPropertyBorderRightColor),
+        borderRightStyle(),
+        borderRightIsTransparent(),
+        !horizontal || includeLogicalRightEdge);
+
+    edges[BSBottom] = BorderEdge(borderBottomWidth(),
+        visitedDependentColor(CSSPropertyBorderBottomColor),
+        borderBottomStyle(),
+        borderBottomIsTransparent(),
+        horizontal || includeLogicalRightEdge);
+
+    edges[BSLeft] = BorderEdge(borderLeftWidth(),
+        visitedDependentColor(CSSPropertyBorderLeftColor),
+        borderLeftStyle(),
+        borderLeftIsTransparent(),
+        !horizontal || includeLogicalLeftEdge);
+}
+
 } // namespace blink