Add required IDL for new error codes

index.bs

@@ -3763,13 +3763,38 @@ please see [[#sctn-create-request-exceptions]] and [[#sctn-get-request-exception
 <xmp class="idl">
 [Exposed=Window, Serializable]
 interface UserCancellationError : DOMException {
+  constructor(optional DOMString message = "");
 };
+</xmp>
+
+The <code>new UserCancellationError(|message|)</code> constructor steps are:
+
+1. Set [=this=]'s {{DOMException/name}} to `"UserCancellationError"`.
+1. Set [=this=]'s {{DOMException/message}} to `message`.
+
+{{UserCancellationError}} objects are [=serializable objects=].
+
+Their [=serialization steps=], given |value| and |serialized|, are to run the {{DOMException}} [=serialization steps=] given |value| and |serialized|.
+
+Their [=deserialization steps=], given |serialized| and |value|, are to run the {{DOMException}} [=deserialization steps=] given |serialized| and |value|.
 
+<xmp class="idl">
 [Exposed=Window, Serializable]
 interface UserVerificationError : DOMException {
+  constructor(optional DOMString message = "");
 };
 </xmp>
 
+The <code>new UserVerificationError(|message|)</code> constructor steps are:
+
+1. Set [=this=]'s {{DOMException/name}} to `"UserVerificationError"`.
+1. Set [=this=]'s {{DOMException/message}} to `message`.
+
+{{UserVerificationError}} objects are [=serializable objects=].
+
+Their [=serialization steps=], given |value| and |serialized|, are to run the {{DOMException}} [=serialization steps=] given |value| and |serialized|.
+
+Their [=deserialization steps=], given |serialized| and |value|, are to run the {{DOMException}} [=deserialization steps=] given |serialized| and |value|.
 
 ## WebAuthn Extensions Inputs and Outputs ## {#sctn-extensions-inputs-outputs}