Fix same-URL navigation session history handling

Closes #6202. Also tidies up the "update the session history with the new page" algorithm more generally, e.g. to be explicit about what session history is being accessed.

source

@@ -84575,6 +84575,15 @@ interface <dfn>Location</dfn> { // but see also <a href="#the-location-interface
     </ol>
    </li>
 
+   <li><p>If <var>historyHandling</var> is "<code data-x="hh-default">default</code>",
+   <var>resource</var> is a <span data-x="concept-request">request</span>, and either
+   <var>resource</var>'s <span data-x="concept-request-url">url</span> <span
+   data-x="concept-url-equals">equals</span> <var>browsingContext</var>'s <span>active
+   document</span>'s <span data-x="concept-document-url">URL</span> or  <var>resource</var>'s <span
+   data-x="concept-request-url">url</span>'s <span data-x="concept-url-scheme">scheme</span> is
+   "<code data-x="javascript protocol">javascript</code>"', then set <var>historyHandling</var> to
+   "<code data-x="hh-replace">replace</code>".</li>
+
    <li><p>Let <var>activeDocumentNavigationOrigin</var> be the <span
    data-x="concept-document-origin">origin</span> of the <span>active document</span> of
    <var>browsingContext</var>.</p></li>
@@ -85557,9 +85566,14 @@ new PaymentRequest(&hellip;); // Allowed to use
   following steps:</p>
 
   <ol>
+   <li><p>Let <var>sessionHistory</var> be <var>navigationParams</var>'s <span
+   data-x="navigation-params-browsing-context">browsing context</span>'s <span>session
+   history</span>.</p></li>
+
    <li>
-    <p><span data-x="unload a document">Unload</span> the <span
-    data-x="she-document">document</span> of the <span>current entry</span>.</p>
+    <p><span data-x="unload a document">Unload</span> <var>sessionHistory</var>'s <span>current
+    entry</span>'s <span
+    data-x="she-document">document</span>.</p>
 
     <p>If this instance of the <span data-x="navigate">navigation</span> algorithm is canceled while
     this step is running the <span>unload a document</span> algorithm, then the <span>unload a
@@ -85570,28 +85584,29 @@ new PaymentRequest(&hellip;); // Allowed to use
    </li>
 
    <li>
-    <dl>
-     <dt>If <var>navigationParams</var>'s <span data-x="navigation-params-hh">history
-     handling</span> is "<code data-x="hh-entry-update">entry update</code>" or "<code
-     data-x="hh-reload">reload</code>"</dt>
-
+    <p>Switch on <var>navigationParams</var>'s <span data-x="navigation-params-hh">history
+     handling</span>:</p>
+    <dl class="switch">
+     <dt>"<code data-x="hh-entry-update">entry update</code>"</dt>
+     <dt>"<code data-x="hh-reload">reload</code>"</dt>
      <dd>
       <ol>
-       <li><p>Replace the <span data-x="she-document">document</span> of the <span>current
-       entry</span>, and of any other entries that reference the same <span
-       data-x="she-document">document</span> as that entry, with <var>newDocument</var>.</p></li>
-
-       <li><p><span>Traverse the history</span> to the <span>current entry</span> with <var
-       data-x="traverse-history-hh">historyHandling</var> set to <var>navigationParams</var>'s <span
-       data-x="navigation-params-hh">history handling</span>.</p></li>
+       <li><p>Let <var>oldDocument</var> be <var>sessionHistory</var>'s <span>current entry</span>'s
+       <span data-x="she-document">document</span>.</p></li>
+
+       <li><p><span data-x="list iterate">For each</span> <var>entry</var> of
+       <var>sessionHistory</var>: if <var>entry</var>'s <span data-x="she-document">document</span>
+       is <var>oldDocument</var>, then set <var>entry</var>'s <span
+       data-x="she-document">document</span> to <var>newDocument</var>.</p></li>
+
+       <li><p><span>Traverse the history</span> to <var>sessionHistory</var>'s <span>current
+       entry</span> with <var data-x="traverse-history-hh">historyHandling</var> set to
+       <var>navigationParams</var>'s <span data-x="navigation-params-hh">history
+       handling</span>.</p></li>
       </ol>
      </dd>
 
-     <dt>Otherwise, if the navigation was initiated with a <span>URL</span> that <span
-     data-x="concept-url-equals">equals</span> <var>navigationParams</var>'s <span
-     data-x="navigation-params-browsing-context">browsing context</span>'s <span>active
-     document</span>'s <span data-x="concept-document-url">URL</span></dt>
-
+     <dt>"<code data-x="hh-replace">replace</code>"</dt>
      <dd>
       <ol>
        <li>
@@ -85600,63 +85615,43 @@ new PaymentRequest(&hellip;); // Allowed to use
         data-x="concept-document-url">URL</span> and <span data-x="she-document">document</span> is
         <var>newDocument</var>.</p>
 
-        <p class="XXX">Some browsers copy over the serialized state of <span>current entry</span>,
-        but this is inconsistent. See <a href="https://github.com/whatwg/html/issues/6213">issue
-        #6213</a> for more discussion on this.</p>
+        <p class="XXX">Some browsers copy over the serialized state <var>sessionHistory</var>'s
+        <span>current entry</span> in cases where its <span data-x="she-URL">URL</span> <span
+        data-x="concept-url-equals">equals</span> that of <var>newDocument</var>, but this is
+        inconsistent. See <a href="https://github.com/whatwg/html/issues/6213">issue #6213</a> for
+        more discussion on this.</p>
        </li>
 
-       <li><p>Insert <var>newEntry</var> after the <span>current entry</span> in
-       <var>navigationParams</var>'s <span data-x="navigation-params-browsing-context">browsing
-       context</span>'s <span>session history</span>.</p></li>
-
-       <li><p><span>Traverse the history</span> to <var>newEntry</var> with <var
-       data-x="traverse-history-hh">historyHandling</var> set to "<code
-       data-x="hh-replace">replace</code>".</p></li>
-      </ol>
-     </dd>
-
-     <dt>Otherwise, if <var>navigationParams</var>'s <span data-x="navigation-params-hh">history
-     handling</span> is "<code data-x="hh-replace">replace</code>"</dt>
-
-     <dd>
-      <ol>
-       <li><p>Let <var>newEntry</var> be a new <span>session history entry</span> whose <span
-        data-x="she-url">URL</span> is <var>newDocument</var>'s <span
-        data-x="concept-document-url">URL</span> and <span data-x="she-document">document</span> is
-        <var>newDocument</var>.</p></li>
-
-       <li><p>Insert <var>newEntry</var> after the <span>current entry</span> in
-       <var>navigationParams</var>'s <span data-x="navigation-params-browsing-context">browsing
-       context</span>'s <span>session history</span>.</p></li>
+       <li><p>Insert <var>newEntry</var> into <var>sessionHistory</var> after its <span>current
+       entry</span>.</p></li>
 
        <li><p><span>Traverse the history</span> to <var>newEntry</var> with
        <var data-x="traverse-history-hh">historyHandling</var> set to "<code
        data-x="hh-replace">replace</code>".</p></li>
       </ol>
      </dd>
 
-     <dt>Otherwise</dt>
-
+     <dt>"<code data-x="hh-default">default</code>"</dt>
      <dd>
       <ol>
-       <li><p>Assert: <var>navigationParams</var>'s <span data-x="navigation-params-hh">history
-       handling</span> is "<code data-x="hh-default">default</code>".</p></li>
-
        <li>
-        <p>Remove all the entries in the <span>session history</span> after the <span>current
-        entry</span>. If the <span>current entry</span> is the last entry in the session history,
-        then no entries are removed.</p>
+        <p>Remove all the entries in <var>sessionHistory</var> after its <span>current entry</span>.
+        (If the <span>current entry</span> is the last entry in the session history, then no entries
+        are removed.)</p>
 
         <p class="note">This <a href="#history-notes">doesn't necessarily have to affect</a> the
         user agent's user interface.</p>
        </li>
 
-       <li><p>Append a new <span>session history entry</span> to the <span>session history</span>,
-       whose <span data-x="she-url">URL</span> is <var>newDocument</var>'s <span
+       <li><p>Let <var>newEntry</var> be a new <span>session history entry</span> whose <span
+       data-x="she-url">URL</span> is <var>newDocument</var>'s <span
        data-x="concept-document-url">URL</span> and <span data-x="she-document">document</span> is
        <var>newDocument</var>.</p></li>
 
-       <li><p><span>Traverse the history</span> to the new entry.</p></li>
+       <li><p><span data-x="list append">Append</span> <var>newEntry</var> to
+       <var>sessionHistory</var>.</p></li>
+
+       <li><p><span>Traverse the history</span> to <var>newEntry</var>.</p></li>
       </ol>
      </dd>
     </dl>