Fragments can only point to nodes in documents

This clarifies that #foo and such can never point to a node in a shadow
tree. Fixes #1192.

source

@@ -82463,11 +82463,11 @@ State: <OUTPUT NAME=I>1</OUTPUT> <INPUT VALUE="Increment" TYPE=BUTTON O
 
   <p><dfn>The indicated part of the document</dfn> is the one that the <span
   data-x="concept-url-fragment">fragment</span>, if any, identifies. The semantics of the <span
-  data-x="concept-url-fragment">fragment</span> in terms of mapping it to a specific DOM Node is
-  defined by the specification that defines the <span>MIME type</span> used by the
-  <code>Document</code> (for example, the processing of <span
-  data-x="concept-url-fragment">fragments</span> for <span
-  data-x="XML MIME type">XML MIME types</span> is the responsibility of RFC7303). <ref spec=RFC7303></p>
+  data-x="concept-url-fragment">fragment</span> in terms of mapping it to a node is defined by the
+  specification that defines the <span>MIME type</span> used by the <code>Document</code> (for
+  example, the processing of <span data-x="concept-url-fragment">fragments</span> for <span
+  data-x="XML MIME type">XML MIME types</span> is the responsibility of RFC7303). <ref
+  spec=RFC7303></p>
 
   <p>For HTML documents (and <span data-x="HTML MIME type">HTML MIME types</span>), the following
   processing model must be followed to determine what <span>the indicated part of the
@@ -82489,14 +82489,16 @@ State: &lt;OUTPUT NAME=I>1&lt;/OUTPUT> &lt;INPUT VALUE="Increment" TYPE=BUTTON O
    fail</span> on <var>fragid bytes</var>. If <var>decoded fragid</var> is failure, jump to the step
    labeled <i>no decoded fragid</i>.</p></li>
 
-   <li><p>If there is an element in the DOM that has an <span data-x="concept-id">ID</span> exactly
-   equal to <var>decoded fragid</var>, then the first such element in <span>tree order</span> is
-   <span>the indicated part of the document</span>; stop the algorithm here.</p></li>
+   <li><p>If there is an element <span data-x="in a document">in the document</span> that has an
+   <span data-x="concept-id">ID</span> exactly equal to <var>decoded fragid</var>, then the first
+   such element in <span>tree order</span> is <span>the indicated part of the document</span>; stop
+   the algorithm here.</p></li>
 
-   <li><p><i>No decoded fragid</i>: If there is an <code>a</code> element in the DOM that has a <code
-   data-x="attr-a-name">name</code> attribute whose value is exactly equal to <var>fragid</var> (<em>not</em> <var>decoded fragid</var>), then the first such
-   element in <span>tree order</span> is <span>the indicated part of the document</span>; stop the algorithm
-   here.</p></li>
+   <li><p><i>No decoded fragid</i>: If there is an <code>a</code> element <span data-x="in a
+   document">in the document</span> that has a <code data-x="attr-a-name">name</code> attribute
+   whose value is exactly equal to <var>fragid</var> (<em>not</em> <var>decoded fragid</var>), then
+   the first such element in <span>tree order</span> is <span>the indicated part of the
+   document</span>; stop the algorithm here.</p></li>
 
    <li><p>If <var>fragid</var> is an <span>ASCII case-insensitive</span> match for the
    string <code data-x="">top</code>, then <span>the indicated part of the document</span> is the top