Don't stretch margin: auto items in a vertical flexbox

Source/core/rendering/RenderBox.cpp

Index: Source/core/rendering/RenderBox.cpp
diff --git a/Source/core/rendering/RenderBox.cpp b/Source/core/rendering/RenderBox.cpp
index 747528e6a35f7bfebec806bbb570a3990b21849a..68af030db0396a7c9d084b607b80e70f66400d87 100644
--- a/Source/core/rendering/RenderBox.cpp
+++ b/Source/core/rendering/RenderBox.cpp
@@ -2229,6 +2229,10 @@ bool RenderBox::sizesLogicalWidthToFitContent(SizeType widthType) const
             return true;
         if (!flexItemHasStretchAlignment(this))
             return true;
+        if (parent()->style()->isColumnFlexDirection() && (style()->marginLeft().isAuto() || style()->marginRight().isAuto())) {
+            // Auto margins means we want centering, not stretching, so we want to return true here
+            return true;
+        }
     }
 
     // Flexible horizontal boxes lay out children at their intrinsic widths.  Also vertical boxes