Re-add early return

Author: lukewarlow

dom.bs

@@ -6549,6 +6549,8 @@ string <var>namespace</var> (default null):</p>
  <var>attr</var>'s <a for=Attr>namespace</a>, <var>attr</var>'s <a for=Attr>local name</a>, and
  <var>element</var>.
 
+ <li><p>If <var>oldAttr</var> is <var>attr</var>, return <var>attr</var>.
+
  <li><p>If <var>oldAttr</var> is non-null, then <a lt="replace an attribute">replace</a>
  <var>oldAttr</var> with <var>attr</var>.