[css-grid] Fix behavior of flexible track breadths

third_party/WebKit/Source/core/layout/LayoutGrid.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 727 matching lines @@
     // If the logical width/height of the grid container is indefinite, percentage values are treated as <auto>
     if (minTrackBreadth.hasPercentage() || maxTrackBreadth.hasPercentage()) {
         if (!hasDefiniteLogicalSize(direction)) {
             if (minTrackBreadth.hasPercentage())
                 minTrackBreadth = Length(Auto);
             if (maxTrackBreadth.hasPercentage())
                 maxTrackBreadth = Length(Auto);
         }
     }
 
+    // Flex sizes are invalid as a min sizing function. However we still can have a flexible |minTrackBreadth|
+    // if the track had a flex size directly (e.g. "1fr"), the spec says that in this case it implies an automatic minimum.
+    if (minTrackBreadth.isFlex())
+        minTrackBreadth = Length(Auto);
+
     return GridTrackSize(minTrackBreadth, maxTrackBreadth);
 }
 
 bool LayoutGrid::isOrthogonalChild(const LayoutBox& child) const
 {
     return child.isHorizontalWritingMode() != isHorizontalWritingMode();
 }
 
 LayoutUnit LayoutGrid::logicalHeightForChild(LayoutBox& child, GridSizingData& sizingData)
 {
@@ skipping 1477 matching lines @@
 
     return LayoutPoint(rowAxisOffset, columnAxisOffsetForChild(child, sizingData));
 }
 
 void LayoutGrid::paintChildren(const PaintInfo& paintInfo, const LayoutPoint& paintOffset) const
 {
     GridPainter(*this).paintChildren(paintInfo, paintOffset);
 }
 
 } // namespace blink