Remove redundant recursive step of fullscreen element ready check (wh…

…atwg#52)

HTML's "allowed to use" only returns true if the document is in the
top-level browsing context, or if it's connected to it via any number of
iframes, all of which must be in a document to have nested browsing
contexts at all, so this final condition would always be true.

Fixes whatwg#50.

fullscreen.bs

@@ -195,11 +195,6 @@ if all of the following are true, and false otherwise:
 
  <li><p><var>element</var>'s <a>node document</a> is <a>allowed to use</a> the feature indicated by
  attribute name <code>allowfullscreen</code>.
-
- <li><p><var>element</var>'s <a>node document</a>'s <a>browsing context</a> either has a
- <a>browsing context container</a> and the <a>fullscreen element ready check</a> returns true for
- <var>element</var>'s <a>node document</a>'s <a>browsing context</a>'s
- <a>browsing context container</a>, or it has no <a>browsing context container</a>.
  <!-- cross-process, recursive -->
 </ul>
 

fullscreen.html

@@ -215,8 +215,6 @@ <h2 class="heading settled" data-level="4" id="api"><span class="secno">4. </spa
     <li>
      <p><var>element</var>’s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#concept-node-document">node document</a> is <a data-link-type="dfn" href="https://html.spec.whatwg.org/multipage/embedded-content.html#allowed-to-use">allowed to use</a> the feature indicated by
  attribute name <code>allowfullscreen</code>. </p>
-    <li>
-     <p><var>element</var>’s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#concept-node-document">node document</a>’s <a data-link-type="dfn" href="https://html.spec.whatwg.org/multipage/browsers.html#browsing-context">browsing context</a> either has a <a data-link-type="dfn" href="https://html.spec.whatwg.org/multipage/browsers.html#browsing-context-container">browsing context container</a> and the <a data-link-type="dfn" href="#fullscreen-element-ready-check">fullscreen element ready check</a> returns true for <var>element</var>’s <a data-link-type="dfn" href="https://dom.spec.whatwg.org/#concept-node-document">node document</a>’s <a data-link-type="dfn" href="https://html.spec.whatwg.org/multipage/browsers.html#browsing-context">browsing context</a>’s <a data-link-type="dfn" href="https://html.spec.whatwg.org/multipage/browsers.html#browsing-context-container">browsing context container</a>, or it has no <a data-link-type="dfn" href="https://html.spec.whatwg.org/multipage/browsers.html#browsing-context-container">browsing context container</a>. </p>
    </ul>
    <p>The <dfn class="idl-code" data-dfn-for="Element" data-dfn-type="method" data-export="" id="dom-element-requestfullscreen"><code>requestFullscreen()</code><a class="self-link" href="#dom-element-requestfullscreen"></a></dfn> method, when invoked, must run
 these steps: </p>