Chrome App webview does not allow access to MessageEvent source in inspector -

i using webview in google chrome app, , when try send message webview parent page, come through, can't access source property send back. have specified origin send parent window origin, , still comes through client, when try inspect in client console, throws error.

webview.addeventlistener('contentload', function() {     webview.contentwindow.postmessage('welcome', window.location.origin); }); 

and in webview:

window.addeventlistener('message', function(event){     console.log(event); }); 

it turned out event.source.postmessage still accessible, couldn't inspect in console.