diff --git a/source b/source
index 5ac4faf7eb7..ea5cd16a5fc 100644
--- a/source
+++ b/source
@@ -96948,10 +96948,10 @@ interface <dfn interface>NotRestoredReasonDetails</dfn> {
 
 [Exposed=Window]
 interface <dfn interface>NotRestoredReasons</dfn> {
-  readonly attribute DOMString? <span data-x="dom-not-restored-reasons-src">src</span>;
+  readonly attribute USVString? <span data-x="dom-not-restored-reasons-src">src</span>;
   readonly attribute DOMString? <span data-x="dom-not-restored-reasons-id">id</span>;
   readonly attribute DOMString? <span data-x="dom-not-restored-reasons-name">name</span>;
-  readonly attribute DOMString? <span data-x="dom-not-restored-reasons-url">url</span>;
+  readonly attribute USVString? <span data-x="dom-not-restored-reasons-url">url</span>;
   readonly attribute FrozenArray&lt;<span>NotRestoredReasonDetails</span>&gt;? <span data-x="dom-not-restored-reasons-reasons">reasons</span>;
   readonly attribute FrozenArray&lt;<span>NotRestoredReasons</span>&gt;? <span data-x="dom-not-restored-reasons-children">children</span>;
   [Default] object toJSON();
@@ -97395,7 +97395,8 @@ interface <dfn interface>NotRestoredReasons</dfn> {
   the following <span data-x="struct item">items</span>:</p>
 
   <ul>
-   <li><p><dfn data-x="nrr-src">src</dfn>, a string or null, initially null.</p></li>
+   <li><p><dfn data-x="nrr-src">src</dfn>, a <span>scalar value string</span> or null, initially
+   null.</p></li>
 
    <li><p><dfn data-x="nrr-id">id</dfn>, a string or null, initially null.</p></li>
 
@@ -104757,22 +104758,38 @@ location.href = '#foo';</code></pre>
    <li><p>Set <var>notRestoredReasonsForDocument</var>'s <span data-x="nrr-url">URL</span> to
    <var>document</var>'s <span data-x="concept-document-url">URL</span>.</p></li>
 
+   <li><p>Let <var>container</var> be <var>document</var>'s <span>node navigable</span>'s <span
+   data-x="nav-container">container</span>.</p></li>
+
    <li>
-    <p>If <var>document</var>'s <span>node navigable</span>'s <span
-    data-x="nav-container">container</span> is an <code>iframe</code> element, then:</p>
+    <p>If <var>container</var> is an <code>iframe</code> element:</p>
 
     <ol>
+     <li><p>Let <var>src</var> be the empty string.</p></li>
+
+     <li>
+      <p>If <var>container</var> has a <code data-x="dom-iframe-src">src</code> attribute:</p>
+
+      <ol>
+       <li><p>Let <var>src</var> be the result of <span>encoding-parsing-and-serializing a
+       URL</span> given <var>container</var>'s <code data-x="attr-iframe-src">src</code> attribute's
+       value, relative to <var>container</var>'s <span>node document</span>.</p></li>
+
+       <li><p>If <var>src</var> is failure, then set <var>src</var> to <var>container</var>'s <code
+       data-x="attr-iframe-src">src</code> attribute's value.</p></li>
+      </ol>
+     </li>
+
      <li><p>Set <var>notRestoredReasonsForDocument</var>'s <span data-x="nrr-src">src</span> to
-     the value of <var>document</var>'s <span>node navigable</span>'s <span
-     data-x="nav-container">container</span>'s <code data-x="attr-iframe-src">src</code> attribute.</p></li>
+     <var>src</var>.</p></li>
 
      <li><p>Set <var>notRestoredReasonsForDocument</var>'s <span data-x="nrr-id">id</span> to
-     the value of <var>document</var>'s <span>node navigable</span>'s <span
-     data-x="nav-container">container</span>'s <code data-x="attr-id">id</code> attribute.</p></li>
+     <var>container</var>'s <code data-x="attr-id">id</code> attribute's value, or the empty string
+     if it has no such attribute.</p></li>
 
-     <li><p>Set <var>notRestoredReasonsForDocument</var>'s <span data-x="nrr-name">name</span>
-     to the value of <var>document</var>'s <span>node navigable</span>'s <span
-     data-x="nav-container">container</span>'s <code data-x="attr-iframe-name">name</code> attribute.</p></li>
+     <li><p>Set <var>notRestoredReasonsForDocument</var>'s <span data-x="nrr-name">name</span> to
+     <var>container</var>'s <code data-x="attr-iframe-name">name</code> attribute's value, or the
+     empty string if it has no such attribute.</p></li>
     </ol>
    </li>