Add pending fullscreen request flag and promise to document state

fullscreen.bs

@@ -67,6 +67,14 @@ stated otherwise it is unset.
 <p>All <a for=/>documents</a> have an associated <dfn>list of pending fullscreen events</dfn>, which
 is an <a>ordered set</a> of (<a>string</a>, <a>element</a>) <a>tuples</a>. It is initially empty.
 
+<p>All <a for=/>documents</a> have an associated <dfn export>pending fullscreen request flag</dfn>.
+Unless stated otherwise it is unset. When set, it indicates that the document has an outstanding
+fullscreen request that has not yet resolved or been rejected.
+
+<p>All <a for=/>documents</a> have an associated <dfn export>pending fullscreen request promise</dfn>.
+Unless stated otherwise it is null. When not null, it is the promise representing the current pending
+fullscreen request.
+
 <p>To <dfn>fullscreen an <var>element</var></dfn>:
 
 <ol>
@@ -266,6 +274,8 @@ are:
 
  <li><p>Let <var>promise</var> be a new promise.
 
+ <li><p>Set <var>pendingDoc</var>'s <a>pending fullscreen request promise</a> to <var>promise</var>.
+
  <li><p>If <var>pendingDoc</var> is not <a>fully active</a>, then reject <var>promise</var> with a
  {{TypeError}} exception and return <var>promise</var>.
 
@@ -294,6 +304,8 @@ are:
  <li><p>If <var>error</var> is false, then <a>consume user activation</a> given
  <var>pendingDoc</var>'s <a>relevant global object</a>.
 
+ <li><p>If <var>error</var> is false, set <var>pendingDoc</var>'s <a>pending fullscreen request</a> flag.
+
  <li><p>Return <var>promise</var>, and run the remaining steps <a>in parallel</a>.
 
  <li>
@@ -342,6 +354,10 @@ are:
   <p>If <var>error</var> is true:
 
   <ol>
+   <li><p>Unset <var>pendingDoc</var>'s <a>pending fullscreen request</a> flag.
+
+   <li><p>Set <var>pendingDoc</var>'s <a>pending fullscreen request promise</a> to null.
+
    <li><p><a for=set>Append</a> ({{fullscreenerror}}, <a>this</a>) to
    <var>pendingDoc</var>'s <a>list of pending fullscreen events</a>.
 
@@ -391,6 +407,10 @@ are:
   <p class=note>The order in which elements are <a lt="fullscreen an element">fullscreened</a>
   is not observable, because <a>run the fullscreen steps</a> is invoked in <a>tree order</a>.
 
+ <li><p>Unset <var>pendingDoc</var>'s <a>pending fullscreen request</a> flag.
+
+ <li><p>Set <var>pendingDoc</var>'s <a>pending fullscreen request promise</a> to null.
+
  <li><p>Resolve <var>promise</var> with undefined.
 </ol>