[css-flexbox] Add issue about resolving unresolvable percentages in flex item contents. (IE already does it.)

Author: tabatkins

css-flexbox/Overview.html

@@ -3222,6 +3222,11 @@ <h3 id=cross-sizing><span class=secno>9.4. </span> Cross Size Determination</h3>
     item</strong> by performing layout with the used main size and the
     available space, treating ‘<code class=css>auto</code>’ as ‘<code
     class=css>fit-content</code>’.
+    <p class="note issue"> Note that if the flex item's cross size is
+     indefinite, any children with percentage cross sizes will be resolved as
+     for ‘<code class=css>auto</code>’. However, if the flex item is
+     ‘<code class=css>align-self: stretch</code>’, these will be resolved
+     in a later step.
 
    <li id=algo-cross-line> <strong>Calculate the cross size of each flex
     line.</strong>
@@ -3289,6 +3294,11 @@ <h3 id=cross-sizing><span class=secno>9.4. </span> Cross Size Determination</h3>
     href="#hypothetical-cross-size"><i>hypothetical cross size</i></a>.
     <p class=note> Note that this step does not affect the main size of the
      flex item, even if it has an intrinsic aspect ratio.
+
+    <p class=issue> Proposed text: If the flex item has ‘<code
+     class=css>align-self: stretch</code>’, redo layout for its contents,
+     treating this used size as its definite cross size so that
+     percentage-sized children can be resolved.
   </ol>
 
   <h3 id=main-alignment><span class=secno>9.5. </span> Main-Axis Alignment</h3>

css-flexbox/Overview.src.html

@@ -2483,6 +2483,12 @@ <h3 id='cross-sizing'>
 			by performing layout with the used main size and the available space,
 			treating ''auto'' as ''fit-content''.
 
+			<p class='note issue'>
+				Note that if the flex item's cross size is indefinite,
+				any children with percentage cross sizes will be resolved as for ''auto''.
+				However, if the flex item is ''align-self: stretch'',
+				these will be resolved in a later step.
+
 		<li id='algo-cross-line'>
 			<strong>Calculate the cross size of each flex line.</strong>
 
@@ -2557,6 +2563,13 @@ <h3 id='cross-sizing'>
 			<p class='note'>
 				Note that this step does not affect the main size of the flex item,
 				even if it has an intrinsic aspect ratio.
+
+			<p class='issue'>
+				Proposed text:
+				If the flex item has ''align-self: stretch'',
+				redo layout for its contents,
+				treating this used size as its definite cross size
+				so that percentage-sized children can be resolved.
 	</ol>
 
 <h3 id='main-alignment'>