Avoid layout/full-repaint on view height change if possible

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 188 matching lines @@
     void removeRenderCounter() { ASSERT(m_renderCounterCount > 0); m_renderCounterCount--; }
     bool hasRenderCounters() { return m_renderCounterCount; }
 
     virtual void addChild(RenderObject* newChild, RenderObject* beforeChild = 0) OVERRIDE;
 
     virtual bool backgroundIsKnownToBeOpaqueInRect(const LayoutRect& localRect) const OVERRIDE FINAL;
 
     double layoutViewportWidth() const;
     double layoutViewportHeight() const;
 
+    void viewResized();
+
 private:
     virtual void mapLocalToContainer(const RenderLayerModelObject* repaintContainer, TransformState&, MapCoordinatesFlags = ApplyContainerFlip, bool* wasFixed = 0) const OVERRIDE;
     virtual const RenderObject* pushMappingToContainer(const RenderLayerModelObject* ancestorToStopAt, RenderGeometryMap&) const OVERRIDE;
     virtual void mapAbsoluteToLocalPoint(MapCoordinatesFlags, TransformState&) const;
     virtual bool requiresColumns(int desiredColumnCount) const OVERRIDE;
     virtual void computeSelfHitTestRects(Vector<LayoutRect>&, const LayoutPoint& layerOffset) const OVERRIDE;
 
     bool initializeLayoutState(LayoutState&);
 
     virtual void calcColumnWidth() OVERRIDE;
@@ skipping 46 matching lines @@
     void releaseWidgets(Vector<RenderWidget*>&);
 
     void pushLayoutStateForCurrentFlowThread(const RenderObject*);
     void popLayoutStateForCurrentFlowThread();
 
     friend class LayoutStateMaintainer;
     friend class LayoutStateDisabler;
 
     bool shouldUsePrintingLayout() const;
 
+    bool needsLayoutOnLogicalHeightChange() const;
+
     FrameView* m_frameView;
 
     RenderObject* m_selectionStart;
     RenderObject* m_selectionEnd;
 
     int m_selectionStartPos;
     int m_selectionEndPos;
 
     int m_maximalOutlineSize; // Used to apply a fudge factor to dirty-rect checks on blocks/tables.
     int m_oldMaximalOutlineSize; // The fudge factor from the previous layout.
@@ skipping 109 matching lines @@
     RenderObject::FlowThreadState m_flowThreadState;
     bool m_fragmenting;
 #ifndef NDEBUG
     LayoutState* m_layoutState;
 #endif
 };
 
 } // namespace WebCore
 
 #endif // RenderView_h