Fail with "no such node" error if origin doesn't match when deserializing a shared reference. (#379)

Author: whimboo

index.bs

@@ -1224,8 +1224,8 @@ To <dfn>deserialize shared reference</dfn> given |shared reference|, |realm| and
    [=realm execution context=]'s Realm component is |realm|.
 
 1. If |node|'s [=node document=]'s [=Document/origin=] is not [=same origin
-   domain=] with |environment settings|'s [=environment settings object/origin=] then
-   return null.
+   domain=] with |environment settings|'s [=environment settings object/origin=]
+   then return [=error=] with [=error code=] [=no such node=].
 
    Note: This ensures that WebDriver-BiDi can not be used to pass objects
    between realms that do not otherwise permit script access.