Add support for parsing <grid-line> that includes a 'span'

Source/core/rendering/RenderGrid.cpp

 /*
  * 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 777 matching lines @@
         // Per http://lists.w3.org/Archives/Public/www-style/2013Mar/0589.html, we clamp negative value to the first line.
         if (endOfTrack < resolvedPosition)
             return 0;
 
         return endOfTrack - resolvedPosition;
     }
     case AutoPosition:
         // 'auto' depends on the opposite position for resolution (e.g. grid-row: auto / 1).
         ASSERT_NOT_REACHED();
         return 0;
+    case SpanPosition:
+        // FIXME: Handle span positions (crbug.com/229713).
+        ASSERT_NOT_REACHED();
+        return 0;
     }
     ASSERT_NOT_REACHED();
     return 0;
 }
 
 LayoutUnit RenderGrid::gridAreaBreadthForChild(const RenderBox* child, TrackSizingDirection direction, const Vector<GridTrack>& tracks) const
 {
     const GridCoordinate& coordinate = cachedGridCoordinate(child);
     const GridSpan& span = (direction == ForColumns) ? coordinate.columns : coordinate.rows;
     LayoutUnit gridAreaBreadth = 0;
@@ skipping 25 matching lines @@
     if (isOutOfFlowPositioned())
         return "RenderGrid (positioned)";
     if (isAnonymous())
         return "RenderGrid (generated)";
     if (isRelPositioned())
         return "RenderGrid (relative positioned)";
     return "RenderGrid";
 }
 
 } // namespace WebCore