[CSS Grid Layout] Fix positioned grid children position and size

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 107 matching lines @@
     LayoutUnit centeredColumnPositionForChild(const RenderBox&) const;
     LayoutUnit columnPositionForChild(const RenderBox&) const;
     LayoutUnit startOfRowForChild(const RenderBox& child) const;
     LayoutUnit endOfRowForChild(const RenderBox& child) const;
     LayoutUnit centeredRowPositionForChild(const RenderBox&) const;
     LayoutUnit rowPositionForChild(const RenderBox&) const;
     LayoutPoint findChildLogicalPosition(const RenderBox&) const;
     GridCoordinate cachedGridCoordinate(const RenderBox&) const;
 
     LayoutUnit gridAreaBreadthForChild(const RenderBox& child, GridTrackSizingDirection, const Vector<GridTrack>&) const;
+    LayoutUnit gridAreaBreadthForPositionedChild(const RenderBox& child, GridTrackSizingDirection, const Vector<GridTrack>&, LayoutUnit& extraInitialOffset) const;
 
     virtual void paintChildren(PaintInfo&, const LayoutPoint&) OVERRIDE;
 
 #if ENABLE(ASSERT)
     bool tracksAreWiderThanMinTrackBreadth(GridTrackSizingDirection, const Vector<GridTrack>&);
 #endif
 
     size_t gridItemSpan(const RenderBox&, GridTrackSizingDirection);
 
     size_t gridColumnCount() const
@@ skipping 16 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