[New Multicolumn] Make computeOffsetFromCompositedAncestor() flowthread-aware.

Source/core/rendering/RenderLayer.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 197 matching lines @@
 
     bool canUseConvertToLayerCoords() const
     {
         // These RenderObjects have an impact on their layers without the renderers knowing about it.
         return !renderer()->hasColumns() && !renderer()->hasTransformRelatedProperty() && !renderer()->isSVGRoot();
     }
 
     void convertToLayerCoords(const RenderLayer* ancestorLayer, LayoutPoint&) const;
     void convertToLayerCoords(const RenderLayer* ancestorLayer, LayoutRect&) const;
 
+    LayoutPoint visualOffsetFromAncestor(const RenderLayer* ancestorLayer) const;
+
     // The hitTest() method looks for mouse events by walking layers that intersect the point from front to back.
     bool hitTest(const HitTestRequest&, HitTestResult&);
     bool hitTest(const HitTestRequest&, const HitTestLocation&, HitTestResult&);
 
     // Pass offsetFromRoot if known.
     bool intersectsDamageRect(const LayoutRect& layerBounds, const LayoutRect& damageRect, const RenderLayer* rootLayer, const LayoutPoint* offsetFromRoot = 0) const;
 
     // Bounding box relative to some ancestor layer. Pass offsetFromRoot if known.
     LayoutRect physicalBoundingBox(const RenderLayer* ancestorLayer, const LayoutPoint* offsetFromRoot = 0) const;
     LayoutRect physicalBoundingBoxIncludingReflectionAndStackingChildren(const RenderLayer* ancestorLayer, const LayoutPoint& offsetFromRoot) const;
@@ skipping 474 matching lines @@
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showLayerTree(const blink::RenderLayer*);
 void showLayerTree(const blink::RenderObject*);
 #endif
 
 #endif // RenderLayer_h