Implement justify-self handling in grid

Source/core/rendering/RenderGrid.h

Index: Source/core/rendering/RenderGrid.h
diff --git a/Source/core/rendering/RenderGrid.h b/Source/core/rendering/RenderGrid.h
index e20a489ec6cd99c0a8f07da3b4d87028059bd08b..24f8f374bb7cbb61a08bdb9d4f86761673d7f507 100644
--- a/Source/core/rendering/RenderGrid.h
+++ b/Source/core/rendering/RenderGrid.h
@@ -112,7 +112,12 @@ private:
     LayoutUnit logicalContentHeightForChild(RenderBox*, Vector<GridTrack>&);
     LayoutUnit minContentForChild(RenderBox*, GridTrackSizingDirection, Vector<GridTrack>& columnTracks);
     LayoutUnit maxContentForChild(RenderBox*, GridTrackSizingDirection, Vector<GridTrack>& columnTracks);
-    LayoutPoint findChildLogicalPosition(RenderBox*, const GridSizingData&);
+    LayoutUnit columnPositionAlignedWithGridContainerStart(const RenderBox*) const;
+    LayoutUnit columnPositionAlignedWithGridContainerEnd(const RenderBox*) const;
+    LayoutUnit centeredColumnPositionForChild(const RenderBox*) const;
+    LayoutUnit columnPositionForChild(const RenderBox*) const;
+    LayoutUnit rowPositionForChild(const RenderBox*) const;
+    LayoutPoint findChildLogicalPosition(const RenderBox*) const;
     GridCoordinate cachedGridCoordinate(const RenderBox*) const;
 
     GridSpan resolveGridPositionsFromAutoPlacementPosition(const RenderBox*, GridTrackSizingDirection, size_t) const;