Add infrastructure for partial layouts

Source/core/rendering/RenderFieldset.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2006, 2009 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 26 matching lines @@
 
 private:
     virtual const char* renderName() const { return "RenderFieldSet"; }
     virtual bool isFieldset() const { return true; }
 
     virtual RenderObject* layoutSpecialExcludedChild(bool relayoutChildren);
 
     virtual void computePreferredLogicalWidths();
     virtual bool avoidsFloats() const { return true; }
 
+    virtual bool supportsPartialLayout() const OVERRIDE { return false; }
+
     virtual void paintBoxDecorations(PaintInfo&, const LayoutPoint&);
     virtual void paintMask(PaintInfo&, const LayoutPoint&);
 };
 
 inline RenderFieldset* toRenderFieldset(RenderObject* object)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isFieldset());
     return static_cast<RenderFieldset*>(object);
 }
 
 // This will catch anyone doing an unnecessary cast.
 void toRenderFieldset(const RenderFieldset*);
 
 } // namespace WebCore
 
 #endif // RenderFieldset_h