Fixes #283 - edit in the second part of the proposal, that auto-min-size only kicks in if you span an auto track.

Author: tabatkins

css-grid/Overview.bs

@@ -1248,7 +1248,8 @@ Implied Minimum Size of Grid Items</h3>
 	that the ''min-width/auto'' value of 'min-width'/'min-height'
 	also applies an <a>automatic minimum size</a>
 	in the specified axis
-	to <a>grid items</a> whose 'overflow' is ''overflow/visible''.
+	to <a>grid items</a> whose 'overflow' is ''overflow/visible''
+	and which span at least one <a>track</a> whose <a>min track sizing function</a> is ''grid-template-rows/auto''.
 	(The effect is analogous to the <a>automatic minimum size</a>
 	imposed on <a>flex items</a>.)
 	[[!CSS-FLEXBOX-1]]