Editorial: use Infra to define the ordered set parser

Found via whatwg/infra#6.

dom.bs

@@ -224,57 +224,21 @@ of <a>preceding</a>
 
 <h3 id="ordered-sets">Ordered sets</h3>
 
-The <dfn export id=concept-ordered-set-parser>ordered set parser</dfn> takes a string
+<p>The <dfn export id=concept-ordered-set-parser>ordered set parser</dfn> takes a string
 <var>input</var> and then runs these steps:
 
 <ol>
- <li>Let <var>position</var> be a pointer into <var>input</var>,
- initially pointing at the start of the string.
+ <li><p>Let <var>inputTokens</var> be the result of
+ <a lt="split on ASCII whitespace">splitting <var>input</var> on ASCII whitespace</a>.
 
- <li>Let <var>tokens</var> be an ordered set of tokens, initially empty.
+ <li><p>Let <var>tokens</var> be a new <a>ordered set</a>.
 
- <li><a>Skip ASCII whitespace</a>.
-
- <li>While <var>position</var> is not past the end of
- <var>input</var>:
-
-  <ol>
-   <li><a>Collect a code point sequence</a> of code points that are
-   not <a>ASCII whitespace</a>.
-
-   <li>If the collected string is not in <var>tokens</var>, append the
-   collected string to <var>tokens</var>.
-
-   <li><a>Skip ASCII whitespace</a>.
-  </ol>
+ <li><p><a for=list>For each</a> <var>token</var> in <var>inputTokens</var>, <a for=set>append</a>
+ <var>token</var> to <var>tokens</var>.
 
  <li>Return <var>tokens</var>.
 </ol>
 
-To <dfn export>collect a code point sequence</dfn> of
-<var>code points</var>, run these steps:
-
-<ol>
- <li>Let <var>input</var> and <var>position</var> be the same
- variables as those of the same name in the algorithm that invoked these
- steps.
-
- <li>Let <var>result</var> be the empty string.
-
- <li>While <var>position</var> does not point past the end of
- <var>input</var> and the code point at <var>position</var> is
- one of <var>code points</var>, append that code point to the end
- of <var>result</var> and advance <var>position</var> to the
- next code point in <var>input</var>.
-
- <li>Return <var>result</var>.
-</ol>
-
-To <dfn export>skip ASCII whitespace</dfn> means to
-<a>collect a code point sequence</a> of
-<a>ASCII whitespace</a> and discard the
-return value.
-
 <p>The <dfn export id=concept-ordered-set-serializer>ordered set serializer</dfn> takes a
 <var>set</var> and returns the concatenation of the strings in <var>set</var>, separated from each
 other by U+0020, if <var>set</var> is non-empty, and the empty string otherwise.