Editorial: formalize the concept of a realm's agent

Follows tc39/ecma262#3058. See tc39/ecma262#1357 for more background.

Adding final step to mask cross-origin

Mask preventedBFCache

Call build nrr for page from unload

fix indentation

Use set to

source

@@ -80509,7 +80509,8 @@ location.href = '#foo';</code></pre>
 
      <li>
       <p>Otherwise, <span>process the next manual redirect</span> for
-      <var>fetchController</var>.</p>
+      <var>fetchController</var>, and set <var>entry</var>'s <span>document state</span>'s <span
+      data-x="document-state-not-restored-reasons">notRestoredReasons</span> to null.</p>
 
       <p class="note">This will result in calling the <i
       data-x="processResponse">processResponse</i> we supplied above, during our first iteration
@@ -82069,6 +82070,80 @@ location.href = '#foo';</code></pre>
   </ol>
 
 
+ <p>To <dfn>build NotRestoredReasons object for page</dfn> given <code>Document state</code>
+ <var>documentState</var>:
+ <ol>
+  <li><p><span>Assert</span>: <var>documentState</var>'s <span
+  data-x="document-state-document">document</span>'s <span>node navigable</span> is a
+  <span>top-level traversable</span>.</p></li>
+
+  <li><p><span>Build NotRestoredReasons object for document</span> given <var>documentState</var>'s
+  <span data-x="document-state-document">document</span>.</p></li>
+
+  <li><p>Count the number of <var>documentState</var>'s <span
+  data-x="document-state-document">document</span>'s <span>descendant navigables</span> whose
+  <span data-x="concept-document-origin">origin</span> is not <span>same origin</span> with
+  <var>documentState</var>'s <span data-x="document-state-document">document</span>.</p>
+
+   <ol>
+    <li><p>Let <var>crossOriginDescendants</var> be an empty <span>list</span>.</p></li>
+
+    <li><p><span data-x="list iterate">For each</span> <var>navigable</var> of
+    <var>documentState</var>'s <span data-x="document-state-document">document</span>'s
+    <span>descendant navigables</span>:</p>
+      <ol>
+       <li><p>If <var>navigable</var>'s <span data-x="nav-document">active document</span>'s
+       <span data-x="concept-document-origin">origin</span> is not <span>same origin</span> with
+       <var>documentState</var>'s <span data-x="document-state-document">document</span>, then <span
+       data-x="list append">append</span> <var>navigable</var> to
+       <var>crossOriginDescendants</var>.</p></li>
+      </ol>
+    </li>
+
+    <li><p>Set <var>crossOriginCount</var> be <var>crossOriginDescendants</var>'s <span
+    data-x="list size">size</span>.</p></li>
+    </ol>
+  </li>
+
+  <li><p>Let <var>randomIndex</var> be a randomly selected integer from 0 to
+  <var>crossOriginCount</var>-1.</p></li>
+
+  <li><p>Let <var>index</var> be 0.</p></li>
+
+  <li><p><span data-x="list iterate">For each</span> <var>navigable</var> of
+  <var>documentState</var>'s <span data-x="document-state-document">document</span>'s
+  <span>descendant navigables</span>:</p>
+   <ol>
+    <li><p>If <var>navigable</var>'s <span data-x="nav-document">active document</span>'s
+    <span data-x="concept-document-origin">origin</span> is not <span>same origin</span> with
+    <var>documentState</var>'s <span data-x="document-state-document">document</span>, then:</p>
+
+     <ol>
+      <li><p>Let <var>reasonsForCrossOriginChild</var> be <var>navigable</var>'s <span
+      data-x="nav-document">active document</span>'s <span>document state</span>'s <span
+      data-x="document-state-not-restored-reasons">notRestoredReasons</span>.</p></li>
+
+      <li><p>Set <var>reasonsForCrossOriginChild</var>'s <span
+      data-x="dom-not-restored-reasons-url">url</span> to null.</p></li>
+
+      <li><p>Set <var>reasonsForCrossOriginChild</var>'s <span
+      data-x="dom-not-restored-reasons-reasons">reasons</span> to null.</p></li>
+
+      <li><p>Set <var>reasonsForCrossOriginChild</var>'s <span
+      data-x="dom-not-restored-reasons-children">children</span> to null.</p></li>
+
+      <li><p>If <var>index</var> is not equal to <var>randomIndex</var>, then set
+      <var>reasonsForCrossOriginChild</var>'s <span
+      data-x="dom-not-restored-reasons-prevented-back-forward-cache">preventedBackForwardCache</span>
+      to "<code data-x="dom-PreventedBackForwardCache-masked">masked</code>".</p></li>
+
+      <li><p>Increment <var>index</var> by 1.</p></li>
+     </ol>
+    </li>
+   </ol>
+  </li>
+ </ol>
+
   <h5>Scrolling to a fragment</h5>
 
   <p>To <dfn id="scroll-to-the-fragment-identifier">scroll to the fragment</dfn> given a
@@ -83220,6 +83295,12 @@ new PaymentRequest(&hellip;); // Allowed to use
    <li><p>Run any <span>unloading document cleanup steps</span> for <var>oldDocument</var> that are
    defined by this specification and <span>other applicable specifications</span>.</p></li>
 
+   <li><p>If <var>oldDocument</var>'s <span>node navigable</span> is a
+   <span>top-level traversable</span>, <span>build NotRestoredReasons object for page</span> given
+   <var>oldDocument</var>'s <span>node navigable</span>'s <span
+   data-x="nav-active-history-entry">active session history entry</span>'s <span
+   data-x="she-document-state">document state</span>.</p></li>
+
    <li><p>If <var>oldDocument</var>'s <i data-x="concept-document-salvageable">salvageable</i> state
    is false, then <span data-x="destroy a document">destroy</span> <var>oldDocument</var>.</p></li>