[css-sizing-4] Update Changes section

Author: fantasai

css-sizing-4/Overview.bs

@@ -714,20 +714,13 @@ Percentage Sizing</h3>
 <h2 class=no-num id="changes">
 Changes</h2>
 
-	<p>
-		Changes since the <a href="https://www.w3.org/TR/2012/WD-css3-sizing-20120927/">September 2012 Working Draft</a> include:
+<h3 class=no-num id="additions-L3">
+Additions Since Level 3</h3>
 
 	<ul>
-		<li>Changed <code>fill</code> keyword to <code>stretch-fit</code>.
-		<li>Hooked up intrinsic sizes of replaced elements to the <a>default sizing algorithm</a> in [[!CSS3-IMAGES]].
-		<li>Specified that <a>extrinsic sizing</a> treates ''margin/auto'' margins as zero.
-		<li>Clarified definition of <a>available space</a>.
-		<li>Specified that percentages resolved against an intrinsic size of the parent computes falls back to auto sizing.
-		<li>Fixed bad wording wrt containing blocks in <a>stretch-fit inline size</a> definition,
-		    and specified that it is calculated <em>after</em> margin collapsing.
-		<li>Specified that an absolutely-positioned box's containing block is always considered definite.
-		<li>Improved section on intrinsic sizing of multi-column containers.
-		<li>Cleaned up some terminology (“min-size” to “min-content size”, “measure” to “inline-size, “extent” to “block-size”).
+		<li>Added ''stretch'', ''fit-content'', and ''contain'' keywords for sizing properties.
+		<li>Added 'aspect-ratio' property.
+		<li>Added 'contain-intrinsic-size' property.
 	</ul>
 
 <h2 class=no-num id="acknowledgments">