nw-tab-capture
Captures web contents as a media stream:
Working with NW.js 0.29.0 pre-release: https://dl.nwjs.io/live-build/nw29/02-27-2018/40fe4d5-0aefc9f-a05c65d-03d4d28/v0.29.0/
See also off-screen tab capture: https://github.com/rogerwang/nw-offscreen-tab