Need to invalidate scrollbars in case they get repositioned.

Source/core/layout/LayoutObject.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 1164 matching lines @@
     // Add hit-test rects for this renderer only to the provided list. layerOffset is the offset
     // of this renderer within the current layer that should be used for each result.
     virtual void computeSelfHitTestRects(Vector<LayoutRect>&, const LayoutPoint& layerOffset) const { };
 
     virtual PaintInvalidationReason paintInvalidationReason(const LayoutLayerModelObject& paintInvalidationContainer,
         const LayoutRect& oldPaintInvalidationRect, const LayoutPoint& oldPositionFromPaintInvalidationBacking,
         const LayoutRect& newPaintInvalidationRect, const LayoutPoint& newPositionFromPaintInvalidationBacking) const;
     virtual void incrementallyInvalidatePaint(const LayoutLayerModelObject& paintInvalidationContainer, const LayoutRect& oldBounds, const LayoutRect& newBounds, const LayoutPoint& positionFromPaintInvalidationBacking);
     void fullyInvalidatePaint(const LayoutLayerModelObject& paintInvalidationContainer, PaintInvalidationReason, const LayoutRect& oldBounds, const LayoutRect& newBounds);
 
+    virtual bool hasNonCompositedScrollbars() const { return false; }
+
 #if ENABLE(ASSERT)
     virtual bool paintInvalidationStateIsDirty() const
     {
         return neededLayoutBecauseOfChildren() || shouldCheckForPaintInvalidationRegardlessOfPaintInvalidationState();
     }
 #endif
 
     virtual void invalidatePaintOfSubtreesIfNeeded(const PaintInvalidationState& childPaintInvalidationState);
     virtual PaintInvalidationReason invalidatePaintIfNeeded(const PaintInvalidationState&, const LayoutLayerModelObject& paintInvalidationContainer);
 
@@ skipping 437 matching lines @@
 void showTree(const blink::LayoutObject*);
 void showLineTree(const blink::LayoutObject*);
 void showRenderTree(const blink::LayoutObject* object1);
 // We don't make object2 an optional parameter so that showRenderTree
 // can be called from gdb easily.
 void showRenderTree(const blink::LayoutObject* object1, const blink::LayoutObject* object2);
 
 #endif
 
 #endif // LayoutObject_h