Fix painting of fixed background images in composited layers

Source/core/rendering/RenderBox.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2006, 2007 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 594 matching lines @@
             removeFloatingOrPositionedChildFromBlockLists();
     }
 
 protected:
     virtual void willBeDestroyed();
 
     virtual void styleWillChange(StyleDifference, const RenderStyle* newStyle);
     virtual void styleDidChange(StyleDifference, const RenderStyle* oldStyle);
     virtual void updateFromStyle() OVERRIDE;
 
-    LayoutRect backgroundPaintedExtent() const;
+    // Returns false if it could not cheaply compute the extent (e.g. fixed background), in which case the returned rect may be incorrect.
+    bool getBackgroundPaintedExtent(LayoutRect&) const;
     virtual bool foregroundIsKnownToBeOpaqueInRect(const LayoutRect& localRect, unsigned maxDepthToTest) const;
     virtual bool computeBackgroundIsKnownToBeObscured() OVERRIDE;
 
     virtual void paintBackgroundWithBorderAndBoxShadow(PaintInfo&, const LayoutRect&, BackgroundBleedAvoidance);
     void paintBackground(const PaintInfo&, const LayoutRect&, BackgroundBleedAvoidance = BackgroundBleedNone);
 
     void paintFillLayer(const PaintInfo&, const Color&, const FillLayer*, const LayoutRect&, BackgroundBleedAvoidance, CompositeOperator, RenderObject* backgroundObject);
     void paintFillLayers(const PaintInfo&, const Color&, const FillLayer*, const LayoutRect&, BackgroundBleedAvoidance = BackgroundBleedNone, CompositeOperator = CompositeSourceOver, RenderObject* backgroundObject = 0);
 
     void paintMaskImages(const PaintInfo&, const LayoutRect&);
@@ skipping 124 matching lines @@
         if (UNLIKELY(m_inlineBoxWrapper != 0))
             deleteLineBoxWrapper();
     }
 
     m_inlineBoxWrapper = boxWrapper;
 }
 
 } // namespace WebCore
 
 #endif // RenderBox_h