Add grid/flex layout support for <fieldset>

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 35 matching lines @@
     ResolveMaxContentMaximums,
     MaximizeTracks,
 };
 enum GridAxisPosition {GridAxisStart, GridAxisEnd, GridAxisCenter};
 
 class LayoutGrid final : public LayoutBlock {
 public:
     explicit LayoutGrid(Element*);
     ~LayoutGrid() override;
 
+    static LayoutGrid* createAnonymous(Document*);
     const char* name() const override { return "LayoutGrid"; }
 
     void layoutBlock(bool relayoutChildren) override;
 
     void dirtyGrid();
 
     Vector<LayoutUnit> trackSizesForComputedStyle(GridTrackSizingDirection) const;
 
     const Vector<LayoutUnit>& columnPositions() const
     {
@@ skipping 172 matching lines @@
 
     std::unique_ptr<OrderedTrackIndexSet> m_autoRepeatEmptyColumns { nullptr };
     std::unique_ptr<OrderedTrackIndexSet> m_autoRepeatEmptyRows { nullptr };
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutGrid, isLayoutGrid());
 
 } // namespace blink
 
 #endif // LayoutGrid_h