[CSS Grid Layout] Remove stack from grid-auto-flow syntax

Source/core/rendering/RenderGrid.h

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 48 matching lines @@
     int paintIndexForGridItem(const RenderBox* renderBox) { return m_gridItemsIndexesMap.get(renderBox); }
 
     bool gridIsDirty() const { return m_gridIsDirty; }
 
 private:
     virtual bool isOfType(RenderObjectType type) const override { return type == RenderObjectRenderGrid || RenderBlock::isOfType(type); }
     virtual void computeIntrinsicLogicalWidths(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth) const override;
     virtual void computePreferredLogicalWidths() override;
 
     virtual void addChild(RenderObject* newChild, RenderObject* beforeChild = 0) override;
-    void addChildToIndexesMap(RenderBox&);
     virtual void removeChild(RenderObject*) override;
 
     virtual void styleDidChange(StyleDifference, const RenderStyle*) override;
 
     bool explicitGridDidResize(const RenderStyle*) const;
     bool namedGridLinesDefinitionDidChange(const RenderStyle*) const;
 
     class GridIterator;
     struct GridSizingData;
     bool gridElementIsShrinkToFit();
@@ skipping 87 matching lines @@
     OrderIterator m_orderIterator;
     Vector<RenderBox*> m_gridItemsOverflowingGridArea;
     HashMap<const RenderBox*, size_t> m_gridItemsIndexesMap;
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderGrid, isRenderGrid());
 
 } // namespace blink
 
 #endif // RenderGrid_h