[CSS Grid Layout] Add support to place items using named grid lines

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 138 matching lines @@
     bool operator==(const GridCoordinate& o) const
     {
         return columns == o.columns && rows == o.rows;
     }
 
     bool operator!=(const GridCoordinate& o) const
     {
         return !(*this == o);
     }
 
+    GridResolvedPosition positionForSide(GridPositionSide side) const
+    {
+        switch (side) {
+        case ColumnStartSide:
+            return columns.resolvedInitialPosition;
+        case ColumnEndSide:
+            return columns.resolvedFinalPosition;
+        case RowStartSide:
+            return rows.resolvedInitialPosition;
+        case RowEndSide:
+            return rows.resolvedFinalPosition;
+        }
+        ASSERT_NOT_REACHED();
+        return 0;
+    }
+
     GridSpan columns;
     GridSpan rows;
 };
 
 typedef HashMap<String, GridCoordinate> NamedGridAreaMap;
 
 } // namespace WebCore
 
 #endif // GridCoordinate_h