[css-flexbox-1] Update changes sectin

Author: fantasai

css-flexbox-1/Overview.bs

@@ -3776,8 +3776,27 @@ Changes since the 16 October 2017 CR</h3>
 				</ul>
 			</blockquote>
 
+		<li id="change-2017-auto-min-zero">
+			Clarified that if the <a>automatic minimum size</a>
+			resolves directly to zero rather than being a <a>content-based minimum size</a>,
+			it does not cause indefiniteness.
+			<blockquote>
+				<p>
+					For the purpose of calculating an intrinsic size of the element
+					(e.g. the element's <a>min-content size</a>),
+					<del>this value</del> <ins>a content-based minimum size</ins>
+					causes the element's size in that axis to become indefinite
+					(even if e.g. its 'width' property specifies a <a>definite</a> size).
+				</p>
+			</blockquote>
+
+		<li id="change-2017-auto-min-size">
+			Editorial improvements to the <a href="#min-size-auto">automatic minimum size</a>.
+			(<a href="https://github.com/w3c/csswg-drafts/issues/2385">Issue 2385</a>)
+
 		<li>
-			Some minor editorial fixes and clarifications.
+			Some minor editorial fixes and clarifications,
+			including updates to vocabulary to match updates to other CSS modules.
 	</ul>
 
 <h3 id="changes-20160526">