Uncaught TypeError: Cannot read property 'WorkflowServicesManager' of undefined from CSOM (NAPA)

SharePoint Online 2013.  Trying to access SP.WorkflowServices.WorkflowServicesManager  from NAPA (CSOM).  Getting error : Cannot read property 'WorkflowServicesManager' of undefined

NAPA App is shared here :  http://aka.ms/V8v2di

We've been able to access the class with PowerShell with no problem.

Here's the code in question:

(function () {

// Getting client context and loading the current web
var context = SP.ClientContext.get_current();
var web = context.get_web();
context.load(web);

// Workflow Services API entry point - WorkflowServiceManager object
var servicesManager = SP.WorkflowServices.WorkflowServicesManager.newObject(context, web);
context.load(servicesManager);

var workflowDefinitions = servicesManager.getWorkflowDeploymentService().enumerateDefinitions(false);
context.load(workflowDefinitions);

context.executeQueryAsync(function (sender, args) {

    // enumerateDefinition returns ClientCollection object
    var definitionsEnum = workflowDefinitions.getEnumerator();

    var empty = true;

    console.log('Site ' + web.get_url() + ':');

    // Going through the definitions
    while (definitionsEnum.moveNext()) {

        var def = definitionsEnum.get_current();

        // Displaying information about this definition - DisplayName and Id
        console.log(def.get_displayName() + " (id: " + def.get_id() + ")");

        empty = false;

    }