Add hasUAVisualTransition to popState and navigate events

Closes #8782.

source

@@ -91612,6 +91612,7 @@ interface <dfn interface>NavigateEvent</dfn> : <span>Event</span> {
   readonly attribute <code>FormData</code>? <span data-x="dom-NavigateEvent-formData">formData</span>;
   readonly attribute DOMString? <span data-x="dom-NavigateEvent-downloadRequest">downloadRequest</span>;
   readonly attribute any <span data-x="dom-NavigateEvent-info">info</span>;
+  readonly attribute boolean <span data-x="dom-NavigateEvent-hasUAVisualTransition">hasUAVisualTransition</span>;
 
   undefined <span data-x="dom-NavigateEvent-intercept">intercept</span>(optional <span>NavigationInterceptOptions</span> options = {});
   undefined <span data-x="dom-NavigateEvent-scroll">scroll</span>();
@@ -91736,6 +91737,11 @@ callback <dfn callback>NavigationInterceptHandler</dfn> = Promise&lt;undefined>
    navigation, or undefined if the navigation was initiated by the user or by a different
    API.</p></dd>
 
+   <dt><code data-x=""><var>event</var>.<span subdfn data-x="dom-NavigateEvent-hasUAVisualTransition">hasUAVisualTransition</span></code></dt>
+   <dd><p>Returns true if the user agent performed a visual transition for this navigation before
+   dispatching this event. If true, the best user experience will be given if the author
+   synchronously updates the DOM to the post-navigation state.</p></dd>
+
    <dt><code data-x=""><var>event</var>.<span subdfn data-x="dom-NavigateEvent-intercept">intercept</span>({ <span subdfn data-x="dom-NavigationInterceptOptions-handler">handler</span>, <span subdfn data-x="dom-NavigationInterceptOptions-focusReset">focusReset</span>, <span subdfn data-x="dom-NavigationInterceptOptions-scroll">scroll</span> })</code></dt>
    <dd>
     <p>Intercepts this navigation, preventing its normal handling and instead converting it into a
@@ -91839,9 +91845,11 @@ callback <dfn callback>NavigationInterceptHandler</dfn> = Promise&lt;undefined>
   for="NavigateEvent"><code data-x="dom-NavigateEvent-signal">signal</code></dfn>, <dfn attribute
   for="NavigateEvent"><code data-x="dom-NavigateEvent-formData">formData</code></dfn>, <dfn
   attribute for="NavigateEvent"><code
-  data-x="dom-NavigateEvent-downloadRequest">downloadRequest</code></dfn>, and <dfn attribute
-  for="NavigateEvent"><code data-x="dom-NavigateEvent-info">info</code></dfn> attributes must return
-  the values they are initialized to.</p>
+  data-x="dom-NavigateEvent-downloadRequest">downloadRequest</code></dfn>, <dfn attribute
+  for="NavigateEvent"><code data-x="dom-NavigateEvent-info">info</code></dfn>, and <dfn attribute
+  for="NavigateEvent"><code
+  data-x="dom-NavigateEvent-hasUAVisualTransition">hasUAVisualTransition</code></dfn> attributes
+  must return the values they are initialized to.</p>
 
   <p>The <dfn method for="NavigateEvent"><code
   data-x="dom-NavigateEvent-intercept">intercept(<var>options</var>)</code></dfn> method steps
@@ -92365,6 +92373,11 @@ interface <dfn interface>NavigationDestination</dfn> {
     tracker</span>.</p>
    </li>
 
+   <li><p>Initialize <var>event</var>'s <code
+   data-x="dom-NavigateEvent-hasUAVisualTransition">hasUAVisualTransition</code> to true if a visual
+   transition, to display a cached rendered state of the <var>document</var>'s <span>latest
+   entry</span>, was done by the user agent. Otherwise, initialize it to false.</p></li>
+
    <li><p>Set <var>event</var>'s <span data-x="concept-NavigateEvent-abort-controller">abort
    controller</span> to a <span>new</span> <code>AbortController</code> created in
    <var>navigation</var>'s <span data-x="concept-relevant-realm">relevant realm</span>.</p></li>
@@ -92878,6 +92891,7 @@ interface <dfn interface>PopStateEvent</dfn> : <span>Event</span> {
   constructor(DOMString type, optional <span>PopStateEventInit</span> eventInitDict = {});
 
   readonly attribute any <span data-x="dom-PopStateEvent-state">state</span>;
+  readonly attribute boolean <span data-x="dom-PopStateEvent-hasUAVisualTransition">hasUAVisualTransition</span>;
 };
 
 dictionary <dfn dictionary>PopStateEventInit</dfn> : <span>EventInit</span> {
@@ -92890,6 +92904,12 @@ dictionary <dfn dictionary>PopStateEventInit</dfn> : <span>EventInit</span> {
    <dd><p>Returns a copy of the information that was provided to <code
    data-x="dom-history-pushState">pushState()</code> or <code
    data-x="dom-history-replaceState">replaceState()</code>.</p></dd>
+
+   <dt><code data-x=""><var>event</var>.<span subdfn data-x="dom-PopStateEvent-hasUAVisualTransition">hasUAVisualTransition</span></code></dt>
+
+   <dd><p>Returns true if the user agent performed a visual transition for this navigation before
+   dispatching this event. If true, the best user experience will be given if the author
+   synchronously updates the DOM to the post-navigation state.</p></dd>
   </dl>
 
   <div w-nodev>
@@ -92899,6 +92919,9 @@ dictionary <dfn dictionary>PopStateEventInit</dfn> : <span>EventInit</span> {
   initialized to. It represents the context information for the event, or null, if the state
   represented is the initial state of the <code>Document</code>.</p>
 
+  <p>The <dfn attribute for="PopStateEvent"><code data-x="dom-PopStateEvent-hasUAVisualTransition">
+  hasUAVisualTransition</code></dfn> attribute must return the value it was initialized to.</p>
+
   </div>
 
 
@@ -99588,7 +99611,10 @@ location.href = '#foo';</code></pre>
        object</span>, using <code>PopStateEvent</code>, with the <code
        data-x="dom-PopStateEvent-state">state</code> attribute initialized to <var>document</var>'s
        <span data-x="doc-history">history object</span>'s <span
-       data-x="concept-history-state">state</span>.</p>
+       data-x="concept-history-state">state</span> and <code
+       data-x="dom-PopStateEvent-hasUAVisualTransition">hasUAVisualTransition</code> initialized to
+       true if a visual transition, to display a cached rendered state of the <span>latest
+       entry</span>, was done by the user agent.</p>
 
        <li><p><span>Restore persisted state</span> given <var>entry</var>.</p></li>
 
@@ -139378,6 +139404,7 @@ INSERT INTERFACES HERE
   Kevin Cole,
   Kevin Gadd,
   Kevin Venkiteswaran,
+  Khushal Sagar,
   Kinuko Yasuda,
   Koji Ishii,
   Korn&eacute;l P&aacute;l,