Ensure positioned descendants are invalidated if needed

Source/core/rendering/RenderObject.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google 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
@@ skipping 1083 matching lines @@
     virtual void incrementallyInvalidatePaint(const RenderLayerModelObject& paintInvalidationContainer, const LayoutRect& oldBounds, const LayoutRect& newBounds, const LayoutPoint& positionFromPaintInvalidationBacking);
     void fullyInvalidatePaint(const RenderLayerModelObject& paintInvalidationContainer, PaintInvalidationReason, const LayoutRect& oldBounds, const LayoutRect& newBounds);
 
 #if ENABLE(ASSERT)
     virtual bool paintInvalidationStateIsDirty() const
     {
         return neededLayoutBecauseOfChildren() || shouldCheckForPaintInvalidationRegardlessOfPaintInvalidationState();
     }
 #endif
 
-    void invalidatePaintOfSubtreesIfNeeded(const PaintInvalidationState&);
+    virtual void invalidatePaintOfSubtreesIfNeeded(const PaintInvalidationState& childPaintInvalidationState);
     virtual PaintInvalidationReason invalidatePaintIfNeeded(const PaintInvalidationState&, const RenderLayerModelObject& paintInvalidationContainer);
 
 private:
     void setLayoutDidGetCalledSinceLastFrame()
     {
         m_bitfields.setLayoutDidGetCalledSinceLastFrame(true);
 
         // Make sure our parent is marked as needing invalidation.
         // This would be unneeded if we allowed sub-tree invalidation (akin to sub-tree layouts).
         markContainingBlockChainForPaintInvalidation();
@@ skipping 421 matching lines @@
 void showTree(const blink::RenderObject*);
 void showLineTree(const blink::RenderObject*);
 void showRenderTree(const blink::RenderObject* object1);
 // We don't make object2 an optional parameter so that showRenderTree
 // can be called from gdb easily.
 void showRenderTree(const blink::RenderObject* object1, const blink::RenderObject* object2);
 
 #endif
 
 #endif // RenderObject_h