ReferenceError: CompositeStream is not defined

[Genie Logiciel]

I need help about CompositeStream class in javascript.

RfbProtocolClient = function() {};
 $prototype = RfbProtocolClient.prototype;
    $prototype.connect = function(url) {
    this.socket = new WebSocket(url);
    this.socket.binaryType = "arraybuffer";
    this.stream = new CompositeStream();
    bindSocketHandlers(this, this.socket);
    this.buttonMask = 0;
    // set first handler
    this.readHandler = versionHandler;
}