function _doLaunchAfterServerReady(initialDoc) {

        _createLiveDocumentForFrame(initialDoc);

        // start listening for requests
        _server.start();

        // open browser to the url
        _open(initialDoc);
    }
@private
Creates the live document in preparation for launching the
preview of the given document, then launches it. (The live document
must already exist before we launch it so that the server can
ask it for the instrumented version of the document when the browser
requests it.)
TODO: could probably just consolidate this with _open()
@param {Document} doc