Make togglePopover() return a boolean

Tests: web-platform-tests/wpt#40409.

Fixes #9043.

source

@@ -11573,7 +11573,7 @@ interface <dfn interface>HTMLElement</dfn> : <span>Element</span> {
   // The popover API
   undefined <span data-x="dom-showPopover">showPopover</span>();
   undefined <span data-x="dom-hidePopover">hidePopover</span>();
-  undefined <span data-x="dom-togglePopover">togglePopover</span>(optional boolean force);
+  boolean <span data-x="dom-togglePopover">togglePopover</span>(optional boolean force);
   [<span>CEReactions</span>] attribute DOMString? <span data-x="dom-popover">popover</span>;
 };
 
@@ -82434,7 +82434,8 @@ dictionary <dfn dictionary>DragEventInit</dfn> : <span>MouseEventInit</span> {
    data-x="dom-togglePopover">togglePopover</span>()</code></dt>
 
    <dd>If the popover <var>element</var> is not showing, then this method shows it. Otherwise, this
-   method hides it.</dd>
+   method hides it. This method returns true if the popover is open after calling it, otherwise
+   false.</dd>
   </dl>
 
   <p>The <dfn method for="HTMLElement"><code data-x="dom-showPopover">showPopover()</code></dfn>
@@ -82721,6 +82722,9 @@ dictionary <dfn dictionary>DragEventInit</dfn> : <span>MouseEventInit</span> {
 
    <li><p>Otherwise, if <var>force</var> is not present or true, then run <span>show popover</span>
    given <span>this</span> true, and null.</p></li>
+
+   <li><p>Return true if <span>this</span>'s <span>popover visibility state</span> is <span
+   data-x="popover-showing-state">showing</span>; otherwise false.</p></li>
   </ol>
 
   <p>To <dfn data-x="hide-all-popovers-until">hide all popovers until</dfn>, given an <span