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

Source/core/rendering/style/GridResolvedPosition.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/rendering/style/GridResolvedPosition.h"
 
 #include "core/rendering/RenderBox.h"
 #include "core/rendering/style/GridCoordinate.h"
 
@@ skipping 29 matching lines @@
     // We must handle the placement error handling code here instead of in the StyleAdjuster because we don't want to
     // overwrite the specified values.
     if (initialPosition.isSpan() && finalPosition.isSpan())
         finalPosition.setAutoPosition();
 
     if (initialPosition.isNamedGridArea() && isNonExistentNamedLineOrArea(initialPosition.namedGridLine(), gridContainerStyle, initialPositionSide))
         initialPosition.setAutoPosition();
 
     if (finalPosition.isNamedGridArea() && isNonExistentNamedLineOrArea(finalPosition.namedGridLine(), gridContainerStyle, finalPositionSide))
         finalPosition.setAutoPosition();
+
+    // If the grid item has an automatic position and a grid span for a named line in a given dimension, instead treat the grid span as one.
+    if (initialPosition.isAuto() && finalPosition.isSpan() && !finalPosition.namedGridLine().isNull())
+        finalPosition.setSpanPosition(1, String());
+    if (finalPosition.isAuto() && initialPosition.isSpan() && !initialPosition.namedGridLine().isNull())
+        initialPosition.setSpanPosition(1, String());
 }
 
 GridSpan GridResolvedPosition::resolveGridPositionsFromAutoPlacementPosition(const RenderStyle& gridContainerStyle, const RenderBox& gridItem, GridTrackSizingDirection direction, const GridResolvedPosition& resolvedInitialPosition)
 {
     GridPosition initialPosition, finalPosition;
     initialAndFinalPositionsFromStyle(gridContainerStyle, gridItem, direction, initialPosition, finalPosition);
 
     GridPositionSide finalPositionSide = calculateFinalPositionSide(direction);
 
     // This method will only be used when both positions need to be resolved against the opposite one.
@@ skipping 166 matching lines @@
 
     // If there is no named grid line of that name, we resolve the position to 'auto' (which is equivalent to 'span 1' in this case).
     // See http://lists.w3.org/Archives/Public/www-style/2013Jun/0394.html.
     if (it == gridLinesNames.end())
         return GridSpan::create(resolvedOppositePosition, resolvedOppositePosition);
 
     return GridSpan::createWithNamedSpanAgainstOpposite(resolvedOppositePosition, position, side, it->value);
 }
 
 } // namespace WebCore