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

Source/core/rendering/style/RenderStyle.h

Index: Source/core/rendering/style/RenderStyle.h
diff --git a/Source/core/rendering/style/RenderStyle.h b/Source/core/rendering/style/RenderStyle.h
index b712ced2c744c0f5c048f66a29d73202f21e68aa..5d02f47100190fc9ef1f6f7d9a477a76fd120163 100644
--- a/Source/core/rendering/style/RenderStyle.h
+++ b/Source/core/rendering/style/RenderStyle.h
@@ -100,6 +100,7 @@ class FilterOperations;
 
 class AppliedTextDecoration;
 class BorderData;
+struct BorderEdge;
 class CounterContent;
 class Font;
 class FontMetrics;
@@ -1536,6 +1537,9 @@ public:
 
     bool hasBoxDecorations() const { return hasBorder() || hasBorderRadius() || hasOutline() || hasAppearance() || boxShadow() || hasFilter(); }
 
+    bool borderObscuresBackground() const;
+    void getBorderEdgeInfo(BorderEdge edges[], bool includeLogicalLeftEdge = true, bool includeLogicalRightEdge = true) const;
+
     // Initial values for all the properties
     static EBorderCollapse initialBorderCollapse() { return BSEPARATE; }
     static EBorderStyle initialBorderStyle() { return BNONE; }