Revert "Remove mention of passing close code or reason to abort() or cancel()"

Put back mention of passing close code or reason to abort() or cancel(),
in preparation for updating it to use WebSocketError.

Author: ricea

index.bs

@@ -876,7 +876,11 @@ initially unset.
    as ArrayBuffer objects.
 
    The stream can be closed by calling {{ReadableStream/cancel()}} on
-   {{WebSocketOpenInfo/readable}}.
+   {{WebSocketOpenInfo/readable}}. If the argument passed to {{ReadableStream/cancel()}} is an
+   object with a {{WebSocketCloseInfo/code}} property and an <span class=allow-2119>optional</span> {{WebSocketCloseInfo/reason}}
+   property then {{WebSocketCloseInfo/code}} will be used as [=the WebSocket connection close
+   code=] and {{WebSocketCloseInfo/reason}} or the empty string will be used as [=the WebSocket
+   connection close reason=].
 
    If no messages are read, or if messages are read slower than they are sent, then backpressure
    will be applied and eventually the server will stop sending new messages.
@@ -889,8 +893,13 @@ initially unset.
    {{WritableStreamDefaultWriter/ready|writer.ready}} promise will ensure that backpressure is
    obeyed.
 
-   The WebSocket can be closed by calling {{WritableStream/close()}} or {{WritableStream/abort()}}
-   on {{WebSocketOpenInfo/writable}}.
+   The WebSocket can be closed by calling {{WritableStream/close()}} on
+   {{WebSocketOpenInfo/writable}}.
+
+   The stream can also be closed by calling {{WritableStream/abort()}}
+   {{WebSocketOpenInfo/writable}}. If an argument is passed to {{WritableStream/abort()}} then it
+   can be used to specify [=the WebSocket connection close code=] and [=the WebSocket connection
+   close reason=] as with {{ReadableStream/cancel()}} above.
 
   : {{WebSocketOpenInfo/extensions}}
   :: The [=extensions in use=] for the connection.