[css-grid] Isolate internal grid size from the actual grid size

third_party/WebKit/Source/core/layout/LayoutGrid.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 327 matching lines @@
   size_t gridColumnCount() const;
   size_t gridRowCount() const;
 
   bool isOrthogonalChild(const LayoutBox&) const;
   GridTrackSizingDirection flowAwareDirectionForChild(
       const LayoutBox&,
       GridTrackSizingDirection) const;
 
   bool cachedHasDefiniteLogicalHeight() const;
 
+  size_t numTracks(GridTrackSizingDirection) const;
+
   typedef Vector<Vector<GridCell>> GridRepresentation;
   GridRepresentation m_grid;
   bool m_gridIsDirty;
   Vector<LayoutUnit> m_rowPositions;
   Vector<LayoutUnit> m_columnPositions;
   LayoutUnit m_offsetBetweenColumns;
   LayoutUnit m_offsetBetweenRows;
   HashMap<const LayoutBox*, GridArea> m_gridItemArea;
   OrderIterator m_orderIterator;
   Vector<LayoutBox*> m_gridItemsOverflowingGridArea;
@@ skipping 14 matching lines @@
   std::unique_ptr<OrderedTrackIndexSet> m_autoRepeatEmptyRows{nullptr};
 
   Optional<bool> m_hasDefiniteLogicalHeight;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutGrid, isLayoutGrid());
 
 }  // namespace blink
 
 #endif  // LayoutGrid_h