[CSS Grid Layout] Update grid-auto-flow to the new syntax

Source/core/rendering/style/StyleGridData.h

 /*
  * Copyright (C) 2011 Google 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 47 matching lines @@
     Vector<GridTrackSize> m_gridTemplateRows;
 
     NamedGridLinesMap m_namedGridColumnLines;
     NamedGridLinesMap m_namedGridRowLines;
 
     // In order to reconstruct the original named grid line order, we can't rely on NamedGridLinesMap
     // as it loses the position if multiple grid lines are set on a single track.
     OrderedNamedGridLines m_orderedNamedGridColumnLines;
     OrderedNamedGridLines m_orderedNamedGridRowLines;
 
-    GridAutoFlow m_gridAutoFlow;
+    unsigned m_gridAutoFlow : GridAutoFlowBits;
 
     GridTrackSize m_gridAutoRows;
     GridTrackSize m_gridAutoColumns;
 
     NamedGridAreaMap m_namedGridArea;
     // Because m_namedGridArea doesn't store the unnamed grid areas, we need to keep track
     // of the explicit grid size defined by both named and unnamed grid areas.
     size_t m_namedGridAreaRowCount;
     size_t m_namedGridAreaColumnCount;
 
 private:
     StyleGridData();
     StyleGridData(const StyleGridData&);
 };
 
 } // namespace WebCore
 
 #endif // StyleGridData_h