[CSS Grid Layout] Named grid line span not allowed for automatic positions

Source/core/rendering/style/GridCoordinate.h

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 96 matching lines @@
         , resolvedFinalPosition(resolvedFinalPosition)
     {
         ASSERT(resolvedInitialPosition <= resolvedFinalPosition);
     }
 
     bool operator==(const GridSpan& o) const
     {
         return resolvedInitialPosition == o.resolvedInitialPosition && resolvedFinalPosition == o.resolvedFinalPosition;
     }
 
+    size_t integerSpan() const
+    {
+        return resolvedFinalPosition.toInt() - resolvedInitialPosition.toInt() + 1;
+    }
+
     GridResolvedPosition resolvedInitialPosition;
     GridResolvedPosition resolvedFinalPosition;
 
     typedef GridResolvedPosition iterator;
 
     iterator begin() const
     {
         return resolvedInitialPosition;
     }
 
@@ skipping 46 matching lines @@
 
     GridSpan columns;
     GridSpan rows;
 };
 
 typedef HashMap<String, GridCoordinate> NamedGridAreaMap;
 
 } // namespace WebCore
 
 #endif // GridCoordinate_h