[css-flexbox] Account for specified size in determining max-content contributions of flex items. Fixes w3c#1435.

Author: fantasai

css-flexbox/Overview.bs

@@ -2843,8 +2843,15 @@ Flex Container Intrinsic Cross Sizes</h4>
 <h4 id='intrinsic-item-contributions'>
 Flex Item Intrinsic Size Contributions</h4>
 
-	The <strong>main-size <a lt="min-content contribution">min-content</a>/<a>max-content contribution</a> of a <a>flex item</a></strong>
-	is its <em>outer</em> <a lt="min-content size">min-content</a>/<a>max-content size</a>,
+	The <strong>main-size <a>min-content contribution</a> of a <a>flex item</a></strong>
+	is its <em>outer</em> <a lt="min-content size">min-content</a>,
+	clamped by its <a>flex base size</a> as a maximum (if it is not growable)
+	and/or as a minimum (if it is not shrinkable),
+	and then further clamped by its <a lt="min main size property">min</a>/<a>max main size properties</a>.
+
+	The <strong>main-size <a>max-content contribution</a> of a <a>flex item</a></strong>
+	is the larger of its <em>outer</em> <a>max-content size</a>
+	and specified size (if that is <a>definite</a>),
 	clamped by its <a>flex base size</a> as a maximum (if it is not growable)
 	and/or as a minimum (if it is not shrinkable),
 	and then further clamped by its <a lt="min main size property">min</a>/<a>max main size properties</a>.
@@ -3413,6 +3420,20 @@ Changes since the 26 May 2016 CR</h3>
 Substantive Changes and Bugfixes</h4>
 
 	<ul>
+		<li id="change-2017-max-contribution">
+			To prevent empty flex items in shrink-to-fit containers
+			from collapsing to zero even when given a specified size,
+			the specified size is now accounted for in calculating
+			its <a>max-content contribution</a> in <a href="#intrinsic-item-contributions"></a>.
+			(<a href="https://github.com/w3c/csswg-drafts/issues/1435">Issue 1435</a>)
+			<blockquote>
+				<p>The <strong>main-size <a>max-content contribution</a> of a <a>flex item</a></strong>
+				is <ins>the larger of</ins> its <em>outer</em> <a>max-content size</a>
+				<ins>and specified size (if that is <a>definite</a>)</ins>,
+				clamped by its <a>flex base size</a> as a maximum (if it is not growable)
+				and/or as a minimum (if it is not shrinkable),
+				and then further clamped by its <a lt="min main size property">min</a>/<a>max main size properties</a>.
+			</blockquote>
 		<li id="change-2016-align-self-as-specified">
 			For ease of implementation, ''align-self/auto'' value of 'align-self' now computes to itself always.
 			See <a href="change-2015-align-self-auto">related previous change</a>