[CSS Grid Layout] Partial implementation of justify-content for Grid.

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 78 matching lines @@
     void placeItemsOnGrid();
     void populateExplicitGridAndOrderIterator();
     PassOwnPtr<GridCoordinate> createEmptyGridAreaAtSpecifiedPositionsOutsideGrid(const RenderBox&, GridTrackSizingDirection, const GridSpan& specifiedPositions) const;
     void placeSpecifiedMajorAxisItemsOnGrid(const Vector<RenderBox*>&);
     void placeAutoMajorAxisItemsOnGrid(const Vector<RenderBox*>&);
     void placeAutoMajorAxisItemOnGrid(RenderBox&, std::pair<size_t, size_t>& autoPlacementCursor);
     GridTrackSizingDirection autoPlacementMajorAxisDirection() const;
     GridTrackSizingDirection autoPlacementMinorAxisDirection() const;
 
     void layoutGridItems();
-    void populateGridPositions(const GridSizingData&);
+    void populateGridPositions(const GridSizingData&, LayoutUnit availableSpaceForColumns, LayoutUnit availableSpaceForRows);
 
     typedef LayoutUnit (RenderGrid::* SizingFunction)(RenderBox&, GridTrackSizingDirection, Vector<GridTrack>&);
     typedef LayoutUnit (GridTrack::* AccumulatorGetter)() const;
     typedef void (GridTrack::* AccumulatorGrowFunction)(LayoutUnit);
     typedef bool (GridTrackSize::* FilterFunction)() const;
     void resolveContentBasedTrackSizingFunctionsForItems(GridTrackSizingDirection, GridSizingData&, GridItemWithSpan&, FilterFunction, SizingFunction, AccumulatorGetter, AccumulatorGrowFunction, FilterFunction growAboveMaxBreadthFilterFunction = nullptr);
     void distributeSpaceToTracks(Vector<GridTrack*>&, Vector<size_t>* tracksForGrowthAboveMaxBreadth, AccumulatorGetter, AccumulatorGrowFunction, GridSizingData&, LayoutUnit& availableLogicalSpace);
 
     double computeNormalizedFractionBreadth(Vector<GridTrack>&, const GridSpan& tracksSpan, GridTrackSizingDirection, LayoutUnit availableLogicalSpace) const;
 
     GridTrackSize gridTrackSize(GridTrackSizingDirection, size_t) const;
 
     LayoutUnit logicalHeightForChild(RenderBox&, Vector<GridTrack>&);
     LayoutUnit minContentForChild(RenderBox&, GridTrackSizingDirection, Vector<GridTrack>& columnTracks);
     LayoutUnit maxContentForChild(RenderBox&, GridTrackSizingDirection, Vector<GridTrack>& columnTracks);
     LayoutUnit startOfColumnForChild(const RenderBox& child) const;
     LayoutUnit endOfColumnForChild(const RenderBox& child) const;
     LayoutUnit columnPositionAlignedWithGridContainerStart(const RenderBox&) const;
     LayoutUnit columnPositionAlignedWithGridContainerEnd(const RenderBox&) const;
     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;
+    LayoutUnit contentPositionAndDistributionOffset(LayoutUnit availableFreeSpace, ContentPosition, ContentDistributionType, unsigned numberOfItems) const;
     LayoutPoint findChildLogicalPosition(const RenderBox&) const;
     GridCoordinate cachedGridCoordinate(const RenderBox&) const;
 
     LayoutUnit gridAreaBreadthForChild(const RenderBox& child, GridTrackSizingDirection, const Vector<GridTrack>&) const;
 
     virtual void paintChildren(PaintInfo&, const LayoutPoint&) override;
     bool needToStretchChildLogicalHeight(const RenderBox&) const;
     LayoutUnit childIntrinsicHeight(const RenderBox&) const;
     LayoutUnit childIntrinsicWidth(const RenderBox&) const;
     LayoutUnit intrinsicLogicalHeightForChild(const RenderBox&) const;
@@ skipping 28 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