Cleanup fullscreen

Fixes https://www.w3.org/Bugs/Public/show_bug.cgi?id=26584 and
https://www.w3.org/Bugs/Public/show_bug.cgi?id=26813. The WHATWG
Fullscreen API standard needs to change “Whenever the unloading
document cleanup steps run with a doc, unfullscreen doc.” to run
fully exit fullscreen. Which in turn should be generalized to
work for all documents and not just the one from the top-level
browsing context.

source

@@ -3121,14 +3121,13 @@ a.setAttribute('href', 'http://example.com/'); // change the content attribute d
 
     <p>The following parts of the WHATWG Fullscreen API standard are referenced from this
     specification, in part to define the rendering of <code>dialog</code> elements, and also to
-    define how the Fullscreen API interacts with the sandboxing features in HTML: <ref
+    define how the Fullscreen API interacts with HTML: <ref
     spec=FULLSCREEN></p>
 
     <ul class="brief">
-     <li>The <dfn data-noexport="">top layer</dfn> concept</li>
-     <li><dfn data-noexport=""><code data-x="dom-element-requestFullscreen">requestFullscreen()</code></dfn>
-     <li>The <dfn data-noexport="">fullscreen enabled flag</dfn></li>
-     <li>The <dfn data-noexport="">fully exit fullscreen</dfn> algorithm</li>
+     <li>The <dfn data-noexport="" data-x-href="https://fullscreen.spec.whatwg.org/#top-layer">top layer</dfn> concept</li>
+     <li><dfn data-noexport="" data-x-href="https://fullscreen.spec.whatwg.org/#dom-element-requestfullscreen"><code data-x="dom-element-requestFullscreen">requestFullscreen()</code></dfn>
+     <li>The <dfn data-noexport="" data-x-href="https://fullscreen.spec.whatwg.org/#fullscreen-enabled-flag">fullscreen enabled flag</dfn></li>
     </ul>
 
     <p>The <cite>High Resolution Time</cite> specification provides the <dfn
@@ -79624,8 +79623,6 @@ callback <dfn>FrameRequestCallback</dfn> = void (<span>DOMHighResTimeStamp</span
 
   <ol>
 
-   <!--TODO: https://www.w3.org/Bugs/Public/show_bug.cgi?id=26584-->
-
    <li><p>Set the <code>Document</code>'s <i
    data-x="concept-document-salvageable">salvageable</i> state to false.</p></li>
 
@@ -81101,8 +81098,6 @@ x === this; // true</pre>
 
       <ol>
 
-       <li><p><span>Fully exit fullscreen</span>.</p></li>
-
        <li><p><span data-x="prompt to unload a document">Prompt to unload</span> the <span>active
        document</span> of the <var>specified browsing context</var>. If the user
        <span>refused to allow the document to be unloaded</span>, then abort these steps.</p></li>
@@ -82745,8 +82740,6 @@ State: &lt;OUTPUT NAME=I>1&lt;/OUTPUT> &lt;INPUT VALUE="Increment" TYPE=BUTTON O
 
    <li>
 
-    <!--TODO: https://www.w3.org/Bugs/Public/show_bug.cgi?id=26584-->
-
     <p><span data-x="unload a document">Unload</span> the <code>Document</code> object of the
     <span>current entry</span>, with the <var>recycle</var> parameter set to false.</p>