private FireFox FindFireFox(Constraint findBy)
        {
            var clientPort = FireFox.GetClientPort();

            clientPort.ConnectToExisting();

            var ffBrowser   = new FFBrowser(clientPort);
            var windowCount = ffBrowser.WindowCount;

            for (var i = 0; i < windowCount; i++)
            {
                ((FireFoxClientPort)ffBrowser.ClientPort).DefineDefaultJSVariablesForWindow(i);
                ffBrowser.ClientPort.InitializeDocument();
                var firefox = CreateBrowserInstance(ffBrowser);
                if (firefox.Matches(findBy))
                {
                    return(firefox);
                }
            }

            clientPort.CloseConnection();

            return(null);
        }