Update to use new "report an exception" algorithm in HTML

It's necessary to specify which global these are reported to. This seems
to be the event listener callback's realm's global in the event listener
case, and the custom element constructor's realm, based on a combination
of consistency with the related sites in HTML and browser behavior --
though browser behavior for custom elements isn't consistent in the
(unusual) case of custom elements across realms.

Part of whatwg/html#10516.

Author: jeremyroman

dom.bs

@@ -1636,10 +1636,13 @@ and an optional <var>legacyOutputDidListenersThrowFlag</var>, run these steps:
    <li>
     <p><a>Call a user object's operation</a> with <var>listener</var>'s
     <a for="event listener">callback</a>, "<code>handleEvent</code>", « <var>event</var> », and
-    <var>event</var>'s {{Event/currentTarget}} attribute value. If this throws an exception, then:
+    <var>event</var>'s {{Event/currentTarget}} attribute value. If this throws an exception
+    <var>exception</var>, then:
 
     <ol>
-     <li><p><a>Report the exception</a>.
+     <li><p><a lt="report an exception">Report</a> <var>exception</var> for <var>listener</var>'s
+     <a for="event listener">callback</a>'s corresponding JavaScript object's
+     <a>associated realm</a>'s <a for="realm">global object</a>.
 
      <li>
       <p>Set <var>legacyOutputDidListenersThrowFlag</var> if given.
@@ -6320,10 +6323,12 @@ given a <var>document</var>, <var>localName</var>, <var>namespace</var>, and opt
      <li><p><a lt="upgrade an element">Upgrade</a> <var>element</var> using <var>definition</var>.
     </ol>
 
-    <p>If this step threw an exception, then:</p>
+    <p>If this step threw an exception <var>exception</var>:
 
     <ol>
-     <li><p><a>Report the exception</a>.
+     <li><p><a lt="report an exception">Report</a> <var>exception</var> for <var>definition</var>'s
+     <a for="custom element definition">constructor</a>'s corresponding JavaScript object's
+     <a>associated realm</a>'s <a for="realm">global object</a>.
 
      <li><p>Set <var>result</var>'s <a for=Element>custom element state</a> to
      "<code>failed</code>".
@@ -6336,7 +6341,7 @@ given a <var>document</var>, <var>localName</var>, <var>namespace</var>, and opt
  </li>
 
  <li>
-  <p>Otherwise, if <var>definition</var> is non-null, then:
+  <p>Otherwise, if <var>definition</var> is non-null:
 
   <ol>
    <li>
@@ -6379,10 +6384,12 @@ given a <var>document</var>, <var>localName</var>, <var>namespace</var>, and opt
      <li><p>Set <var>result</var>'s <a for=Element><code>is</code> value</a> to null.
     </ol>
 
-    <p>If any of these steps threw an exception, then:</p>
+    <p>If any of these steps threw an exception <var>exception</var>:
 
     <ol>
-     <li><p><a>Report the exception</a>.
+     <li><p><a lt="report an exception">Report</a> <var>exception</var> for <var>definition</var>'s
+     <a for="custom element definition">constructor</a>'s corresponding JavaScript object's
+     <a>associated realm</a>'s <a for="realm">global object</a>.
 
      <li><p>Set <var>result</var> to a new <a for=/>element</a> that implements the
      {{HTMLUnknownElement}} interface, with no attributes, <a for=Element>namespace</a> set to the