correct shadow root registry inheritance and constructor map

dom.bs

@@ -2843,12 +2843,22 @@ before a <var>child</var>, with an optional <i>suppress observers flag</i>, run
         <a>upgrade an element</a> algorithm.
       </ol>
 
-     <li><p>If <var>inclusiveDescendant</var> is <a>connected</a> and is a <a for=/>shadow root</a>
-     whose <a for=ShadowRoot>custom element registry</a> is null, then set
-     <var>inclusiveDescendant</var>'s <a for=ShadowRoot>custom element registry</a> to the result of
-     <b>looking up a custom element registry</b> given <var>inclusiveDescendant</var>'s
-     <a for=tree>parent</a>.
-     <!-- XXX xref -->
+     <li>
+      <p>Otherwise, if all of the following are true:
+
+      <ul class=brief>
+       <li><var>inclusiveDescendant</var> is <a>connected</a>,
+       <li><var>inclusiveDescendant</var> is a <a for=/>shadow root</a>,
+       <li><var>inclusiveDescendant</var>'s <a for=ShadowRoot>custom element registry</a> is null,
+       and
+       <li><var>inclusiveDescendant</var>'s <a for=ShadowRoot>keep custom element registry null</a>
+       is false,
+      </ul>
+
+      <p>then set <var>inclusiveDescendant</var>'s <a for=ShadowRoot>custom element registry</a> to
+      the result of <b>looking up a custom element registry</b> given
+      <var>inclusiveDescendant</var>'s <a for=DocumentFragment>host</a>.
+      <!-- XXX xref -->
     </ol>
   </ol>
 
@@ -6092,22 +6102,23 @@ enum SlotAssignmentMode { "manual", "named" };
 <p>{{ShadowRoot}} <a for=/>nodes</a> are simply known as
 <dfn export id=concept-shadow-root lt="shadow root">shadow roots</dfn>.
 
+<p><a for=/>Shadow roots</a>'s associated <a for=DocumentFragment>host</a> is never null.</p>
+<!-- If we ever change this, e.g., add a ShadowRoot object constructor, that would have serious
+     consequences for innerHTML. -->
+
 <p><a for=/>Shadow roots</a> have an associated <dfn for=ShadowRoot>mode</dfn> ("<code>open</code>"
 or "<code>closed</code>").</p>
 
-<p><a for=/>Shadow roots</a> have an associated <dfn export for=ShadowRoot>delegates focus</dfn>.
-It is initially set to false.</p>
+<p><a for=/>Shadow roots</a> have an associated <dfn export for=ShadowRoot>delegates focus</dfn>
+(a boolean). It is initially set to false.</p>
 
 <p><a for=/>Shadow roots</a> have an associated
-<dfn export for=ShadowRoot>available to element internals</dfn>. It is initially set to false.</p>
+<dfn export for=ShadowRoot>available to element internals</dfn> (a boolean). It is initially set to
+false.</p>
 
 <p><a for=/>Shadow roots</a> have an associated <dfn export for=ShadowRoot>declarative</dfn>
 (a boolean). It is initially set to false.</p>
 
-<p><a for=/>Shadow roots</a>'s associated <a for=DocumentFragment>host</a> is never null.</p>
-<!-- If we ever change this, e.g., add a ShadowRoot object constructor, that would have serious
-     consequences for innerHTML. -->
-
 <p><a for=/>Shadow roots</a> have an associated <dfn for=ShadowRoot>slot assignment</dfn>
 ("<code>manual</code>" or "<code>named</code>").
 
@@ -6120,6 +6131,15 @@ It is initially set to false.</p>
 <p><a for=/>Shadow roots</a> have an associated <dfn for=ShadowRoot>custom element registry</dfn>
 (null or a {{CustomElementRegistry}} object).</p>
 
+<p><a for=/>Shadow roots</a> have an associated
+<dfn for=ShadowRoot>keep custom element registry null</dfn> (a boolean). It is initially false.
+
+<p class=note>This can only ever be true in combination with declarative shadow roots. And it only
+matters for as long as the <a for=/>shadow root</a>'s <a for=ShadowRoot>custom element registry</a>
+is null.
+
+<hr>
+
 <p>A <a for=/>shadow root</a>'s <a>get the parent</a> algorithm, given an <var>event</var>, returns
 null if <var>event</var>'s <a>composed flag</a> is unset and <a for=/>shadow root</a> is the
 <a for=tree>root</a> of <var>event</var>'s <a for=Event>path</a>'s first struct's
@@ -6312,7 +6332,7 @@ dictionary ShadowRootInit {
  "<code>precustomized</code>", or "<code>custom</code>".
 
  <dt><dfn export id=concept-element-custom-element-definition for=Element>custom element definition</dfn>
- <dd>Null or a <b for=/>custom element definition</b>.
+ <dd>Null or a <b>custom element definition</b>.
  <!-- XXX xref -->
 
  <dt><dfn export id=concept-element-is-value for=Element><code>is</code> value</dfn>
@@ -6461,7 +6481,7 @@ null), boolean <var>synchronousCustomElements</var> (default false), and null or
      <li><p>Let <var>C</var> be <var>definition</var>'s
      <a for="custom element definition">constructor</a>.
 
-     <li><p><a for=map>Set</a> <var>registry</var>'s <a>relevant global object</a>'s
+     <li><p><a for=map>Set</a> the <a>surrounding agent</a>'s
      <b>active custom element constructor map</b>[<var>C</var>] to <var>registry</var>.
      <!-- XXX xref -->
 
@@ -6517,7 +6537,7 @@ null), boolean <var>synchronousCustomElements</var> (default false), and null or
       </ol>
 
      <li>
-      <p><a for=map>Remove</a> <var>registry</var>'s <a>relevant global object</a>'s
+      <p><a for=map>Remove</a> the <a>surrounding agent</a>'s
       <b>active custom element constructor map</b>[<var>C</var>].
       <!-- XXX xref -->