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

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 106 matching lines @@
 
     TrackedRendererListHashSet* positionedObjects() const;
     bool hasPositionedObjects() const
     {
         TrackedRendererListHashSet* objects = positionedObjects();
         return objects && !objects->isEmpty();
     }
 
     void addPercentHeightDescendant(RenderBox*);
     static void removePercentHeightDescendant(RenderBox*);
-    TrackedRendererListHashSet* percentHeightDescendants() const;
     static bool hasPercentHeightContainerMap();
     static bool hasPercentHeightDescendant(RenderBox*);
     static void clearPercentHeightDescendantsFrom(RenderBox*);
     static void removePercentHeightDescendantIfNeeded(RenderBox*);
 
+    TrackedRendererListHashSet* percentHeightDescendants() const;
+    bool hasPercentHeightDescendants() const
+    {
+        TrackedRendererListHashSet* descendants = percentHeightDescendants();
+        return descendants && !descendants->isEmpty();
+    }
+
     void setHasMarkupTruncation(bool b) { m_hasMarkupTruncation = b; }
     bool hasMarkupTruncation() const { return m_hasMarkupTruncation; }
 
     void setHasMarginBeforeQuirk(bool b) { m_hasMarginBeforeQuirk = b; }
     void setHasMarginAfterQuirk(bool b) { m_hasMarginAfterQuirk = b; }
 
     bool hasMarginBeforeQuirk() const { return m_hasMarginBeforeQuirk; }
     bool hasMarginAfterQuirk() const { return m_hasMarginAfterQuirk; }
 
     bool hasMarginBeforeQuirk(const RenderBox* child) const;
@@ skipping 572 matching lines @@
     // FIXME: This is temporary as we move code that accesses block flow
     // member variables out of RenderBlock and into RenderBlockFlow.
     friend class RenderBlockFlow;
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderBlock, isRenderBlock());
 
 } // namespace WebCore
 
 #endif // RenderBlock_h