[css-flexbox] Clarify that an intrinsic min size makes the size indefinite while calculating intrinsic sizes. Resolves

https://drafts.csswg.org/css-flexbox-1/issues-cr-2016#3

Author: tabatkins

css-flexbox/Overview.bs

@@ -941,6 +941,17 @@ Implied Minimum Size of Flex Items</h3>
 					and then further clamped by the <a>max main size property</a> if that is <a>definite</a>.
 			</dl>
 
+			For the purpose of calculating an intrinsic size of the element
+			(e.g. the element's <a>min-content size</a>),
+			this value causes the element's width/height to become indefinite
+			(even if e.g. its 'width' property specifies a <a>definite</a> size).
+			Note this means that percentages calculated against this size
+			will be treated as ''height/auto''.
+			Otherwise, although this may require an additional layout pass to re-resolve percentages in some cases,
+			this value
+			(like the ''min-content'', ''max-content'', and ''fit-content'' values defined in [[CSS3-SIZING]])
+			does not prevent the resolution of percentage sizes within the item.
+
 			Otherwise,
 			this keyword computes to ''0''
 			(unless otherwise defined by a future specification).
@@ -964,10 +975,6 @@ Implied Minimum Size of Flex Items</h3>
 		this traversal is trivial and therefore not a performance concern.)
 	</div>
 
-	Although this may require an additional layout pass to re-resolve percentages in some cases,
-	the ''min-width/auto'' value of 'min-width' and 'min-height'
-	(like the ''min-content'', ''max-content'', and ''fit-content'' values defined in [[CSS3-SIZING]])
-	does not prevent the resolution of percentage sizes within the item.
 
 <h2 id="flow-order">
 Ordering and Orientation</h2>