Suggest using the Cookie Store API instead of document.cookie

Fixes #11658.

Author: Chanran

source

@@ -11156,6 +11156,12 @@ partial interface <dfn id="document" data-lt="">Document</dfn> {
   attribute represents the cookies of the resource identified by the document's <span
   data-x="concept-document-url">URL</span>.</p>
 
+  <p class="note">Using the synchronous <code data-x="dom-document-cookie">document.cookie</code>
+  API can be a source of performance issues. The <cite>Cookie Store API</cite> can be used instead,
+  as it provides an asynchronous way to handle cookies to avoid performance issues. See the <a
+  href="https://cookiestore.spec.whatwg.org/#intro">Cookie Store API introduction</a> for more
+  information. <ref>COOKIESTORE</ref></p>
+
   <p>A <code>Document</code> object that falls into one of the following conditions is a
   <dfn>cookie-averse <code>Document</code> object</dfn>:</p>
 
@@ -149937,6 +149943,9 @@ INSERT INTERFACES HERE
    <dt id="refsCOOKIES">[COOKIES]</dt>
    <dd><cite><a href="https://httpwg.org/specs/rfc6265.html">HTTP State Management Mechanism</a></cite>, A. Barth. IETF.</dd>
 
+   <dt id="refsCOOKIESTORE">[COOKIESTORE]</dt>
+   <dd>(Non-normative) <cite><a href="https://cookiestore.spec.whatwg.org/">Cookie Store API</a></cite>, J. Wilcock, M. Nottingham. WHATWG.</dd>
+
    <dt id="refsCREDMAN">[CREDMAN]</dt>
    <dd><cite><a href="https://w3c.github.io/webappsec-credential-management/">Credential Management</a></cite>, N. Satragno, J. Hodges, M. West. W3C.</dd>