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

Source/core/paint/BoxDecorationData.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BoxDecorationData_h
+#define BoxDecorationData_h
+
+#include "core/rendering/RenderBoxModelObject.h"
+#include "platform/graphics/Color.h"
+
+namespace blink {
+
+class RenderStyle;
+class GraphicsContext;
+
+// Information extracted from RenderStyle for box painting.
+class BoxDecorationData {

[pdr., 2014/09/09 20:45:42]

I feel like this is more of a struct than a class.

[chrishtr, 2014/09/09 22:38:18]

Has public and private? I don't really have much of an opinion either way.

+public:
+    BoxDecorationData(const RenderStyle&, bool canRenderBorderImage, bool backgroundHasOpaqueTopLayer, GraphicsContext*);
+
+    Color backgroundColor;
+    bool hasBackground;
+    bool hasBorder;
+    bool hasAppearance;
+    BackgroundBleedAvoidance bleedAvoidance;

[pdr., 2014/09/09 20:45:42]

Save 4 bytes with this one weird trick!

BackgroundBleedAvoidance bleedAvoidance : 2;
(it actually is weird)

[chrishtr, 2014/09/09 22:38:18]

Done

+
+private:
+    BackgroundBleedAvoidance determineBackgroundBleedAvoidance(const RenderStyle&, bool canRenderBorderImage, bool backgroundHasOpaqueTopLayer, GraphicsContext*);
+    bool borderObscuresBackgroundEdge(const RenderStyle&, const FloatSize& contextScale) const;
+};
+
+} // namespace blink
+
+#endif