Merge pull request #558 from christiaanbrand/patch-2

Plumb User ID through

index.bs

@@ -945,6 +945,9 @@ When this method is invoked, the user agent MUST execute the following algorithm
                 : {{AuthenticatorAssertionResponse/signature}}
                 :: A new {{ArrayBuffer}}, created using |global|'s [=%ArrayBuffer%=], containing the bytes of the returned
                     {{signature}}
+                : {{AuthenticatorAssertionResponse/userId}}
+                :: A new {{DOMString}} containing the user handle returned from the successful [=authenticatorGetAssertion=] operation, 
+                    as defined in [[#op-get-assertion]].   
             :   {{PublicKeyCredential/clientExtensionResults}}
             ::  A new {{AuthenticationExtensions}} object containing the [=extension identifier=] → [=client extension output=]
                 entries created by running each extension's [=client extension processing=] algorithm to create the [=client
@@ -1062,6 +1065,7 @@ optionally evidence of [=user consent=] to a specific transaction.
     interface AuthenticatorAssertionResponse : AuthenticatorResponse {
         [SameObject] readonly attribute ArrayBuffer      authenticatorData;
         [SameObject] readonly attribute ArrayBuffer      signature;
+        [SameObject] readonly attribute DOMString        userId;
     };
 </pre>
 <div dfn-type="attribute" dfn-for="AuthenticatorAssertionResponse">
@@ -1740,6 +1744,7 @@ On successful completion, the authenticator returns to the user agent:
 - The identifier of the credential (credential ID) used to generate the [=assertion signature=].
 - The [=authenticator data=] used to generate the [=assertion signature=].
 - The [=assertion signature=].
+- The user handle associated with the credential used to generate the [=assertion signature=].
 
 If the authenticator cannot find any credential corresponding to the specified [=[RP]=] that matches the specified criteria, it
 terminates the operation and returns an error.