Add "hide all popovers" algorithm for Fullscreen

This also fixes a bug where a null endpoint is passed to hide all popovers until, but hide all popovers until assumes endpoint is not null by looking for endpoint's node document. The bug is fixed by letting hide all popovers until take a document.

And it also exports some definitions for Fullscreen.

Corresponding Fullscreen PR: whatwg/fullscreen#204.

Author: josepharhar

source

@@ -59985,8 +59985,8 @@ interface <dfn interface>HTMLDialogElement</dfn> : <span>HTMLElement</span> {
   and a boolean <var>isModal</var>, are as follows:</p>
 
   <ol>
-   <li><p>Run <span data-x="hide-all-popovers-until">hide all popovers until</span> given null,
-   false, and true.</p></li>
+   <li><p>Run <span>hide all popovers</span> given <var>subject</var>'s <span>node
+   document</span>.</p></li>
 
    <li><p>Let <var>control</var> be null.</p></li>
 
@@ -81743,14 +81743,16 @@ dictionary <dfn dictionary>DragEventInit</dfn> : <span>MouseEventInit</span> {
   must <span>reflect</span> the <span data-x="attr-popover">popover</span> attribute, <span>limited
   to only known values</span>.</p>
 
-  <p>Every <span data-x="HTML elements">HTML element</span> has a <dfn>popover visibility
+  <p>Every <span data-x="HTML elements">HTML element</span> has a <dfn export>popover visibility
   state</dfn>, initially <span data-x="popover-hidden-state">hidden</span>, with these potential
   values:</p>
 
   <ul>
-   <li><p><dfn data-x="popover-hidden-state">hidden</dfn></p></li>
+   <li><p><dfn export for="popover visibility state"
+   data-x="popover-hidden-state">hidden</dfn></p></li>
 
-   <li><p><dfn data-x="popover-showing-state">showing</dfn></p></li>
+   <li><p><dfn export for="popover visibility state"
+   data-x="popover-showing-state">showing</dfn></p></li>
   </ul>
 
   <p>The <code>Document</code> has an <dfn>auto popover list</dfn>, which is a <span>list</span>,
@@ -81876,6 +81878,9 @@ dictionary <dfn dictionary>DragEventInit</dfn> : <span>MouseEventInit</span> {
      <li><p>Let <var>ancestor</var> be the result of running the <span>topmost popover
      ancestor</span> algorithm given <var>element</var>.</p></li>
 
+     <li><p>If <var>ancestor</var> is null, then set <var>ancestor</var> to
+     <var>document</var>.</p></li>
+
      <li><p>Run <span data-x="hide-all-popovers-until">hide all popovers until</span> given
      <var>ancestor</var>, false, and true.</p></li>
 
@@ -82094,7 +82099,7 @@ dictionary <dfn dictionary>DragEventInit</dfn> : <span>MouseEventInit</span> {
   </ol>
 
   <p>To <dfn data-x="hide-all-popovers-until">hide all popovers until</dfn>, given an <span
-  data-x="HTML elements">HTML element</span> <var>endpoint</var>, a boolean
+  data-x="HTML elements">HTML element</span> or <code>Document</code> <var>endpoint</var>, a boolean
   <var>focusPreviousElement</var>, and a boolean <var>fireEvents</var>:</p>
 
   <ol>
@@ -82161,6 +82166,10 @@ dictionary <dfn dictionary>DragEventInit</dfn> : <span>MouseEventInit</span> {
   happens. For example, during light-dismiss of a popover, this algorithm ensures that we close only
   the popovers that aren't related to the node clicked by the user.</p>
 
+  <p>To <dfn export>hide all popovers</dfn>, given a <code>Document</code> <var>document</var>, run
+  <span data-x="hide-all-popovers-until">hide all popovers until</span> given <var>document</var>,
+  false, and false.</p>
+
   <p>To find the <dfn>topmost popover ancestor</dfn>, given a <code>Node</code>
   <var>newPopover</var>, perform the following steps. They return an <span data-x="HTML
   elements">HTML element</span> or null.</p>
@@ -82558,6 +82567,9 @@ dictionary <dfn dictionary>DragEventInit</dfn> : <span>MouseEventInit</span> {
 
      <li><p>Set <var>document</var>'s <span>popover pointerdown target</span> to null.</p></li>
 
+     <li><p>If <var>ancestor</var> is null, then set <var>ancestor</var> to
+     <var>document</var>.</p></li>
+
      <li><p>If <var>sameTarget</var> is true, then run <span data-x="hide-all-popovers-until">hide
      all popovers until</span> given <var>ancestor</var>, false, and true.</p></li>
     </ol>