Add infrastructure for partial layouts

Source/core/rendering/RenderBlock.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 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 479 matching lines @@
             m_rareData->m_discardMarginBefore = false;
             m_rareData->m_discardMarginAfter = false;
         }
     }
 
     virtual void layout();
 
     void layoutPositionedObjects(bool relayoutChildren, bool fixedPositionObjectsOnly = false);
     void markFixedPositionObjectForLayoutIfNeeded(RenderObject* child);
 
+    // FIXME: This should be pure virtual with an implementation in the header.
+    virtual bool supportsPartialLayout() const OVERRIDE { return true; };
+
     virtual void paint(PaintInfo&, const LayoutPoint&);
     virtual void paintObject(PaintInfo&, const LayoutPoint&);
     virtual void paintChildren(PaintInfo&, const LayoutPoint&);
     void paintChild(RenderBox*, PaintInfo&, const LayoutPoint&);
 
     LayoutUnit logicalRightOffsetForLine(LayoutUnit logicalTop, LayoutUnit fixedOffset, bool applyTextIndent, LayoutUnit* heightRemaining = 0, LayoutUnit logicalHeight = 0) const
     {
         return adjustLogicalRightOffsetForLine(logicalRightFloatOffsetForLine(logicalTop, fixedOffset, heightRemaining, logicalHeight, ShapeOutsideFloatShapeOffset), applyTextIndent);
     }
     LayoutUnit logicalLeftOffsetForLine(LayoutUnit logicalTop, LayoutUnit fixedOffset, bool applyTextIndent, LayoutUnit* heightRemaining = 0, LayoutUnit logicalHeight = 0) const
@@ skipping 837 matching lines @@
     static String string(const int value);
 };
 template<> struct ValueToString<RenderBlock::FloatingObject*> {
     static String string(const RenderBlock::FloatingObject*);
 };
 #endif
 
 } // namespace WebCore
 
 #endif // RenderBlock_h