The live demo does not work on chrome

Hello,

I am running a couple of chrome browsers on different laptops and the demo is not working.
http://khan.github.io/live-editor/demos/simple/

In the console I get this error:

`Uncaught TypeError: Cannot freeze
at Function.freeze ()
at child.bind (live-editor.output_pjs.js:1451)
at child.initialize (live-editor.output_pjs.js:1287)
at child.Backbone.View (live-editor.core_deps.js:27944)
at new child (live-editor.core_deps.js:28488)
at child.setOutput (live-editor.output.js:367)
at child.handleMessage (live-editor.output.js:429)`

On Firefox it works just fine. Is the problem in my browsers? I am using it often and I need to know if it is going to work on chrome? Because on most laptops we have Chrome.

Reproduce the failure at the live demo URL in Chrome and compare it with Firefox. Start with the stack-trace locations in live-editor.output_pjs.js, live-editor.core_deps.js, and live-editor.output.js; done means the demo initializes in Chrome without the reported TypeError.

Written by the indexing model from the issue text.