diff --git a/source b/source
index ad70ef70bfc..02a921ea340 100644
--- a/source
+++ b/source
@@ -76515,8 +76515,8 @@ dictionary <dfn>DragEventInit</dfn> : <span>MouseEventInit</span> {
     </ul>
    </li>
 
-   <li><p><span>Set up a browsing context environment settings object</span> with
-   <var>realm execution context</var>.</p></li>
+   <li><p><span>Set up a browsing context environment settings object</span> with <var>realm
+   execution context</var>, and let <var>settingsObject</var> be the result.</p></li>
 
    <li><p>Let <var>document</var> be a new <code>Document</code>, marked as an <span data-x="HTML
    documents">HTML document</span> in <span>quirks mode</span>, whose <span
@@ -76560,6 +76560,9 @@ dictionary <dfn>DragEventInit</dfn> : <span>MouseEventInit</span> {
 
    <li><p><span>Implement the sandboxing</span> for <var>document</var>.</p></li>
 
+   <li><p>Set <var>settingsObject</var>'s <span
+   data-x="concept-environment-execution-ready-flag">execution ready flag</span>.</p></li>
+
    <li><p>Add <var>document</var> to <var>browsingContext</var>'s <span>session
    history</span>.</p></li>
 
@@ -81795,6 +81798,9 @@ State: &lt;OUTPUT NAME=I>1&lt;/OUTPUT> &lt;INPUT VALUE="Increment" TYPE=BUTTON O
 
      <li><p><span>Implement the sandboxing</span> for the <code>Document</code>.</p></li>
 
+     <li><p>Set <var>settingsObject</var>'s <span
+     data-x="concept-environment-execution-ready-flag">execution ready flag</span>.</p></li>
+
      <li>
       <p>If <var>settingsObject</var>'s <span
       data-x="concept-environment-active-service-worker">active service worker</span> is not null,
@@ -85798,6 +85804,11 @@ interface <dfn>NavigatorOnLine</dfn> {
    data-dfn-for="environment">active service worker</dfn></dt>
    <dd><p>Null or a <span data-x="dfn-service-worker">service worker</span> that <span
    data-x="dfn-control">controls</span> the <span>environment</span>.</p></dd>
+
+   <dt>An <dfn data-x="concept-environment-execution-ready-flag" data-export=""
+   data-dfn-for="environment">execution ready flag</dfn></dt>
+   <dd><p>A flag that indicates whether the environment setup is done. It is initially
+   unset.</p></dd>
   </dl>
 
   <p>An <dfn data-export="">environment settings object</dfn> is an <span>environment</span> that
@@ -96360,6 +96371,9 @@ interface <dfn>SharedWorkerGlobalScope</dfn> : <span>WorkerGlobalScope</span> {
 
    </li>
 
+   <li><p>Set <var>inside settings</var>'s <span
+   data-x="concept-environment-execution-ready-flag">execution ready flag</span>.</p></li>
+
    <!-- SCRIPT EXEC -->
 
    <li>