Allow grid positions to be named grid areas

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 978 matching lines @@
 
         size_t resolvedPosition = abs(position.integerPosition()) - 1;
         const size_t endOfTrack = explicitGridSizeForSide(side);
 
         // 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 adjustGridPositionForSide(endOfTrack - resolvedPosition, side);
     }
+    case NamedGridAreaPosition:
+        // FIXME: Support resolving named grid area (crbug.com/258092).
+        return 0;
     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).
+        // 'auto' and span depend on the opposite position for resolution (e.g. grid-row: auto / 1 or grid-column: span 3 / "myHeader").
         ASSERT_NOT_REACHED();
         return 0;
     }
     ASSERT_NOT_REACHED();
     return 0;
 }
 
 PassOwnPtr<GridSpan> RenderGrid::resolveGridPositionAgainstOppositePosition(size_t resolvedOppositePosition, const GridPosition& position, GridPositionSide side) const
 {
     if (position.isAuto())
@@ skipping 106 matching lines @@
     if (isOutOfFlowPositioned())
         return "RenderGrid (positioned)";
     if (isAnonymous())
         return "RenderGrid (generated)";
     if (isRelPositioned())
         return "RenderGrid (relative positioned)";
     return "RenderGrid";
 }
 
 } // namespace WebCore