[css-flexbox] While the intrinsic sizing steps here guarantee that we're larger than the min-size prior to clamping by the max-size, the max-size could be less than the min-size. Therefore floor at the min-size when clamping. Fixes #361.

Author: fantasai

css-flexbox/Overview.bs

@@ -2786,7 +2786,8 @@ Flex Container Intrinsic Main Sizes</h4>
 			to the product of its <a>flex grow factor</a>
 			(or <a>scaled flex shrink factor</a>, if the chosen <var>max-content flex fraction</var> was negative)
 			and the chosen <var>max-content flex fraction</var>,
-			then clamp that result by the <a>max main size property</a>.
+			then clamp that result by the <a>max main size property</a>
+			floored by the <a>min main size property</a>.
 
 		<li>
 			The <a>flex container</a>’s <a>max-content size</a> is the
@@ -3440,6 +3441,20 @@ Substantive Changes and Bugfixes</h4>
 				a value of ''align-self: auto'' is treated identically to ''align-self/start''<ins>,
 				and ''margin/auto'' margins are treated as zero</ins>.</p>
 			</blockquote>
+		<li>When clamping by the <a>max main size property</a>
+			in the <a href="#intrinsic-main-sizes">calculation of the flex container’s intrinsic size</a>,
+			be sure to floor by the <a>min main size property</a>.
+			<blockquote>
+				<p>Within each line,
+				find the largest <var>max-content flex fraction</var>
+				among all the <a>flex items</a>.
+				Add each item’s <a>flex base size</a>
+				to the product of its <a>flex grow factor</a>
+				(or <a>scaled flex shrink factor</a>, if the chosen <var>max-content flex fraction</var> was negative)
+				and the chosen <var>max-content flex fraction</var>,
+				then clamp that result by the <a>max main size property</a>
+				<ins>floored by the <a>min main size property</a></ins>.</p>
+			</blockquote>
 	</ul>
 
 <h4 id="change-201605-clarify">