Update element adoption logic for scoped registries

Fixes #1429 by making sure elements get the correct scoped custom
element registry upon adoption.

Author: Jayson Chen

dom.bs

@@ -4872,7 +4872,7 @@ and an optional <a for=/>document</a> <dfn export for="clone a node"><var>docume
 
    <li><p>If <var>shadowRootRegistry</var> <a>is a global custom element registry</a>, then set
    <var>shadowRootRegistry</var> to <var>document</var>'s
-   <a>effective global custom element registry</a>.
+   <a for=Document>custom element registry</a>'s <a>effective global custom element registry</a>.
 
    <li><p><a>Attach a shadow root</a> with <var>copy</var>, <var>node</var>'s
    <a for=Element>shadow root</a>'s <a for=ShadowRoot>mode</a>, true, <var>node</var>'s
@@ -4917,7 +4917,8 @@ and an optional <a for=/>document</a> <dfn export for="clone a node"><var>docume
    <var>fallbackRegistry</var>.
 
    <li><p>If <var>registry</var> <a>is a global custom element registry</a>, then set
-   <var>registry</var> to <var>document</var>'s <a>effective global custom element registry</a>.
+   <var>registry</var> to <var>document</var>'s <a for=Document>custom element registry</a>'s
+   <a>effective global custom element registry</a>.
 
    <li><p>Set <var>copy</var> to the result of <a>creating an element</a>, given
    <var>document</var>, <var>node</var>'s <a for=Element>local name</a>, <var>node</var>'s
@@ -6047,7 +6048,8 @@ algorithm is passed <var ignore>node</var> and <var ignore>oldDocument</var>, as
     </ul>
 
     <p>then set <var>inclusiveDescendant</var>'s <a for=ShadowRoot>custom element registry</a> to
-    <var>document</var>'s <a>effective global custom element registry</a>.
+    <var>document</var>'s <a for=Document>custom element registry</a>'s
+    <a>effective global custom element registry</a>.
 
    <li>
     <p>Otherwise, if <var>inclusiveDescendant</var> is an <a for=/>element</a>:
@@ -6056,11 +6058,27 @@ algorithm is passed <var ignore>node</var> and <var ignore>oldDocument</var>, as
      <li><p>Set the <a for=Node>node document</a> of each <a>attribute</a> in
      <var>inclusiveDescendant</var>'s <a for=Element>attribute list</a> to <var>document</var>.
 
-     <li><p>If <var>inclusiveDescendant</var>'s <a for=Element>custom element registry</a> is null
-     or <var>inclusiveDescendant</var>'s <a for=Element>custom element registry</a>'s
-     <a for=CustomElementRegistry>is scoped</a> is false, then set
-     <var>inclusiveDescendant</var>'s <a for=Element>custom element registry</a> to
-     <var>document</var>'s <a>effective global custom element registry</a>.
+     <li>
+      <p>If <var>inclusiveDescendant</var>'s <a for=Element>custom element registry</a> is null or
+      <var>inclusiveDescendant</var>'s <a for=Element>custom element registry</a>'s
+      <a for=CustomElementRegistry>is scoped</a> is false:
+
+      <ol>
+       <li><p>Let <var>registry</var> be null.
+
+       <li><p>If <var>inclusiveDescendant</var>'s <a for=Element>custom element registry</a> is
+       non-null, <var>inclusiveDescendant</var>'s <a for=tree>parent</a> is null, or
+       <var>inclusiveDescendant</var>'s <a for=tree>parent</a> is an
+       <a>exclusive <code>DocumentFragment</code> node</a>, then set <var>registry</var> to
+       <var>document</var>'s <a for=Document>custom element registry</a>.
+
+       <li><p>Otherwise, set <var>registry</var> to the result of
+       <a for=/>looking up a custom element registry</a> given <var>inclusiveDescendant</var>'s
+       <a for=tree>parent</a>.
+
+       <li><p>Set <var>inclusiveDescendant</var>'s <a for=Element>custom element registry</a> to
+       <var>registry</var>'s <a>effective global custom element registry</a>.
+      </ol>
 
      <li><p>If <var>inclusiveDescendant</var> is <a for=Element>custom</a>, then
      <a>enqueue a custom element callback reaction</a> with <var>inclusiveDescendant</var>, callback
@@ -6099,13 +6117,12 @@ algorithm is passed <var ignore>node</var> and <var ignore>oldDocument</var>, as
 <dfn>is a global custom element registry</dfn> if <var>registry</var> is non-null and
 <var>registry</var>'s <a for=CustomElementRegistry>is scoped</a> is false.</p>
 
-<p>A <a for=/>document</a> <var>document</var>'s <dfn>effective global custom element registry</dfn>
-is:
+<p>Null or a {{CustomElementRegistry}} object <var>registry</var>'s
+<dfn>effective global custom element registry</dfn> is:
 
 <ol>
- <li><p>If <var>document</var>'s <a for=Document>custom element registry</a>
- <a>is a global custom element registry</a>, then return <var>document</var>'s
- <a for=Document>custom element registry</a>.
+ <li><p>If <var>registry</var> <a>is a global custom element registry</a>, then return
+ <var>registry</var>.
 
  <li><p>Return null.
 </ol>
@@ -6449,30 +6466,43 @@ interface DocumentFragment : Node {
 };
 </pre>
 
+<dl class=domintro>
+ <dt><code><var ignore>tree</var> = new {{DocumentFragment()}}</code>
+ <dd>Returns a new {{DocumentFragment}} <a for=/>node</a>.
+</dl>
+
+<hr>
+
+<div algorithm>
+<p>An <dfn export>exclusive {{DocumentFragment}} node</dfn> is a {{DocumentFragment}}
+<a for=/>node</a> that is not a {{ShadowRoot}} <a for=/>node</a>.
+</div>
+
 <p>A {{DocumentFragment}} <a for=/>node</a> has an associated
 <dfn export id=concept-documentfragment-host for=DocumentFragment>host</dfn> (null or an
 <a for=/>element</a> in a different <a>node tree</a>). It is null unless otherwise stated.
 
+<div algorithm>
 <p>An object <var>A</var> is a
 <dfn export id=concept-tree-host-including-inclusive-ancestor>host-including inclusive ancestor</dfn>
 of an object <var>B</var>, if either <var>A</var> is an <a for=tree>inclusive ancestor</a> of <var>B</var>,
 or if <var>B</var>'s <a for=tree>root</a> has a non-null <a for=DocumentFragment>host</a> and
 <var>A</var> is a <a>host-including inclusive ancestor</a> of <var>B</var>'s <a for=tree>root</a>'s
 <a for=DocumentFragment>host</a>.
+</div>
 
 <p class=note>The {{DocumentFragment}} <a for=/>node</a>'s <a for=DocumentFragment>host</a>
 concept is useful for HTML's <{template}> element and for <a for=/>shadow roots</a>, and impacts the
 <a>pre-insert</a> and <a>replace</a> algorithms.
 
-<dl class=domintro>
- <dt><code><var ignore>tree</var> = new {{DocumentFragment()}}</code>
- <dd>Returns a new {{DocumentFragment}} <a for=/>node</a>.
-</dl>
+<hr>
 
+<div algorithm>
 <p>The
 <dfn constructor for=DocumentFragment lt=DocumentFragment()><code>new DocumentFragment()</code></dfn>
 constructor steps are to set <a>this</a>'s <a for=Node>node document</a> to
 <a>current global object</a>'s <a>associated <code>Document</code></a>.
+</div>
 
 
 <h3 id=interface-shadowroot>Interface {{ShadowRoot}}</h3>