Shadow: adjust composedPath() when currentTarget is a Window object

Fixes #326.

dom.bs

@@ -745,9 +745,19 @@ steps:
  <li>
   <p>For each <var>tuple</var> in <a>context object</a>'s <a for=Event>path</a>:
 
-  <ol><li><p>If <var>currentTarget</var> is a <a>node</a> and <var>tuple</var>'s <b>item</b> is not
-  <a>closed-shadow-hidden</a> from <var>currentTarget</var>, or <var>currentTarget</var> is not a
-  <a>node</a>, then append <var>tuple</var>'s <b>item</b> to <var>composedPath</var>.</p></li></ol>
+  <ol>
+   <li>
+    <p>If <var>currentTarget</var> is a {{Window}} object, then:
+
+    <ol><li><p>If <var>tuple</var>'s <b>item</b> is not a <a>node</a>, or <var>tuple</var>'s
+    <b>item</b> is not <a>closed-shadow-hidden</a> from <var>tuple</var>'s <b>item</b>'s
+    <a>shadow-including root</a>, then append <var>tuple</var>'s <b>item</b> to
+    <var>composedPath</var>.</p></li></ol>
+
+   <li><p>Otherwise, if <var>currentTarget</var> is a <a>node</a> and <var>tuple</var>'s <b>item</b>
+   is not <a>closed-shadow-hidden</a> from <var>currentTarget</var>, or <var>currentTarget</var> is
+   not a <a>node</a>, then append <var>tuple</var>'s <b>item</b> to <var>composedPath</var>.
+  </ol>
 
  <li><p>Return <var>composedPath</var>.
 </ol>
@@ -4564,7 +4574,7 @@ The <dfn attribute for=Document><code>URL</code></dfn> attribute's getter and
 <a for=Document>URL</a>, <a lt="URL serializer" spec=url>serialized</a>.
 
 The <dfn attribute for=Document><code>origin</code></dfn> attribute's getter must return the
-<a lt="Unicode serialisation of an origin">Unicode serialization</a> of <a>context object</a>'s
+<a lt="Unicode serialization of an origin">Unicode serialization</a> of <a>context object</a>'s
 <a for=Document>origin</a>.
 
 The <dfn attribute for=Document><code>compatMode</code></dfn> attribute's getter must