Add infrastructure for partial layouts

Source/core/rendering/RenderView.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 41 matching lines @@
     virtual bool isRenderView() const OVERRIDE { return true; }
 
     virtual bool requiresLayer() const OVERRIDE { return true; }
 
     virtual bool isChildAllowed(RenderObject*, RenderStyle*) const OVERRIDE;
 
     virtual void layout() OVERRIDE;
     virtual void updateLogicalWidth() OVERRIDE;
     virtual void computeLogicalHeight(LayoutUnit logicalHeight, LayoutUnit logicalTop, LogicalExtentComputedValues&) const OVERRIDE;
 
+    virtual bool supportsPartialLayout() const OVERRIDE { return true; }
+
     virtual LayoutUnit availableLogicalHeight(AvailableLogicalHeightType) const OVERRIDE;
 
     // The same as the FrameView's layoutHeight/layoutWidth but with null check guards.
     int viewHeight() const;
     int viewWidth() const;
     int viewLogicalWidth() const { return style()->isHorizontalWritingMode() ? viewWidth() : viewHeight(); }
     int viewLogicalHeight() const;
 
     float zoomFactor() const;
 
@@ skipping 323 matching lines @@
     RenderObject::FlowThreadState m_flowThreadState;
     bool m_fragmenting;
 #ifndef NDEBUG
     LayoutState* m_layoutState;
 #endif
 };
 
 } // namespace WebCore
 
 #endif // RenderView_h