*** NOT FOR LANDING *** mapLocalToContainer and offsetFromContainer cleanup.

Source/core/layout/LayoutBoxModelObject.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2006, 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 165 matching lines @@
     virtual LayoutUnit containingBlockLogicalWidthForContent() const;
 
     virtual void childBecameNonInline(LayoutObject* /*child*/) { }
 
     virtual bool boxShadowShouldBeAppliedToBackground(BackgroundBleedAvoidance, InlineFlowBox* = nullptr) const;
 
     // Overridden by subclasses to determine line height and baseline position.
     virtual LayoutUnit lineHeight(bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const = 0;
     virtual int baselinePosition(FontBaseline, bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const = 0;
 
+    virtual LayoutSize offsetFromContainer(const LayoutObject*) const override;
     virtual void mapAbsoluteToLocalPoint(MapCoordinatesFlags, TransformState&) const override;
     virtual const LayoutObject* pushMappingToContainer(const LayoutBoxModelObject* ancestorToStopAt, LayoutGeometryMap&) const override;
 
     virtual void setSelectionState(SelectionState) override;
 
     void contentChanged(ContentChangeType);
     bool hasAcceleratedCompositing() const;
 
     virtual void computeLayerHitTestRects(LayerHitTestRects&) const override;
 
@@ skipping 70 matching lines @@
     virtual bool isBoxModelObject() const override final { return true; }
 
     OwnPtr<DeprecatedPaintLayer> m_layer;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutBoxModelObject, isBoxModelObject());
 
 } // namespace blink
 
 #endif // LayoutBoxModelObject_h