[css-grid] Fix simplified layout of positioned grid items

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 156 matching lines @@
                                           LayoutUnit& maxIntrinsicSize) const;
   LayoutUnit computeTrackBasedLogicalHeight(const GridSizingData&) const;
   void computeTrackSizesForDefiniteSize(GridTrackSizingDirection,
                                         GridSizingData&,
                                         LayoutUnit freeSpace) const;
 
   void repeatTracksSizingIfNeeded(GridSizingData&,
                                   LayoutUnit availableSpaceForColumns,
                                   LayoutUnit availableSpaceForRows);
 
+  bool simplifiedLayout() override;
   void layoutGridItems(GridSizingData&);
   void prepareChildForPositionedLayout(LayoutBox&);
-  void layoutPositionedObjects(bool relayoutChildren,
-                               PositionedLayoutBehavior = DefaultLayout);
+  void layoutPositionedObjects(
+      bool relayoutChildren,
+      PositionedLayoutBehavior = DefaultLayout) override;
   void offsetAndBreadthForPositionedChild(const LayoutBox&,
                                           GridTrackSizingDirection,
                                           LayoutUnit& offset,
                                           LayoutUnit& breadth);
   void populateGridPositionsForDirection(GridSizingData&,
                                          GridTrackSizingDirection);
 
   typedef struct GridItemsSpanGroupRange GridItemsSpanGroupRange;
   LayoutUnit currentItemSizeForTrackSizeComputationPhase(
       TrackSizeComputationPhase,
@@ skipping 173 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