File input dialog not shown with CrossWalk project

Question

I've built a simple (content entirely remote) app with CrossWalk. In the app there is a <input type="file"> element for uploading photos. But the usual dialog for selecting photo album doesn't show up.

To experiment, I made a minimum app with the same tag in index.html and it works. So I'm lost.

My app has a index.js that navigate to an external web site like this:

onDeviceReady: function() {
    // window.open = cordova.InAppBrowser.open;
    ref = window.open('http://foo.com', '_blank', 'location=no,toolbar=no,hardwareback=no');
},

In the real page, there is a similar input box but when tapping on it, nothing happens.

ps. I'm using plupload. Not sure if it has anything to do with it.