Remove margin collapsing.

sky/engine/core/rendering/RenderBox.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2006, 2007 Apple Inc. 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 285 matching lines @@
     {
         const RenderStyle* styleToUse = overrideStyle ? overrideStyle : style();
         m_marginBox.setStart(styleToUse->direction(), value);
     }
     void setMarginEnd(LayoutUnit value, const RenderStyle* overrideStyle = 0)
     {
         const RenderStyle* styleToUse = overrideStyle ? overrideStyle : style();
         m_marginBox.setEnd(styleToUse->direction(), value);
     }
 
-    // The following five functions are used to implement collapsing margins.
-    // All objects know their maximal positive and negative margins.  The
-    // formula for computing a collapsed margin is |maxPosMargin| - |maxNegmargin|.
-    // For a non-collapsing box, such as a leaf element, this formula will simply return
-    // the margin of the element.  Blocks override the maxMarginBefore and maxMarginAfter
-    // methods.
-    enum MarginSign { PositiveMargin, NegativeMargin };
-    virtual bool isSelfCollapsingBlock() const { return false; }
-    virtual LayoutUnit collapsedMarginBefore() const { return marginBefore(); }
-    virtual LayoutUnit collapsedMarginAfter() const { return marginAfter(); }
-
     virtual void absoluteRects(Vector<IntRect>&, const LayoutPoint& accumulatedOffset) const override;
     virtual void absoluteQuads(Vector<FloatQuad>&) const override;
 
     virtual void layout() override;
     virtual void paint(PaintInfo&, const LayoutPoint&) override;
     virtual bool nodeAtPoint(const HitTestRequest&, HitTestResult&, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction) override;
 
     virtual LayoutUnit minPreferredLogicalWidth() const override;
     virtual LayoutUnit maxPreferredLogicalWidth() const override;
 
@@ skipping 409 matching lines @@
         if (UNLIKELY(inlineBoxWrapper() != 0))
             deleteLineBoxWrapper();
     }
 
     ensureRareData().m_inlineBoxWrapper = boxWrapper;
 }
 
 } // namespace blink
 
 #endif // RenderBox_h