[css-grid] Fix the sizing of auto tracks when the grid is min/max-content.

Author: tabatkins

css-grid/Overview.bs

@@ -3427,7 +3427,13 @@ Resolve Intrinsic Track Sizes</h3>
 					to the maximum of the items’ <a>max-content contributions</a>.
 				<li>
 					<strong>For auto minimums:</strong>
-					If the track has an ''auto'' <a>min track sizing function</a>,
+					If the track has an ''auto'' <a>min track sizing function</a>
+					and the <a>grid container</a> is being sized under a <a lt="min-content constraint">min/max-content constraint</a>,
+					set the track's <a>base size</a>
+					to the maximum of its items’ <a lt="min-content contribution">min/max-content contributions</a>,
+					respectively.
+
+					Otherwise,
 					set its <a>base size</a>
 					to the maximum of its items’ “min-size contributions”:
 					the value specified by its respective 'min-width' or 'min-height' properties