Expose window.External

Hiding interface objects is no longer a thing the web platform does.

Helps with whatwg/webidl#430.

Author: annevk

source

@@ -116060,8 +116060,7 @@ interface <dfn>HTMLFontElement</dfn> : <span>HTMLElement</span> {
   <p>The <dfn><code data-x="dom-external">external</code></dfn> attribute of the <code>Window</code>
   interface must return an instance of the <code>External</code> interface:</p>
 
-  <pre><code class="idl" data-x="">[Exposed=Window,
- NoInterfaceObject]
+  <pre><code class="idl" data-x="">[Exposed=Window]
 interface <dfn>External</dfn> {
   void <span data-x="dom-external-AddSearchProvider">AddSearchProvider</span>();
   void <span data-x="dom-external-IsSearchProviderInstalled">IsSearchProviderInstalled</span>();