DOWNstream For Electron 
DOWNstream is an open-source plugin to use with Electron allowing encrypted MPEG-DASH and Smooth Streaming streams to be safely downloaded and stored locally on a user’s Windows or Mac computer.
Installation
npm install downstream-electron --save
Main process
Renderer process
See available configuration
castLabs Electron Release for Content Security
To simplify the use of Widevine DRM and allow protected playback of offline content within Electron CastLabs has created a fork with support for Widevine CDM installation, Verified Media Path (VMP), and protected storage of offline licenses. Such a release is installed by the default npm package scripts.
More information is available here:
https://github.com/castlabs/electron-releases
License
Copyright (C) 2017 Castlabs GmbH. Licensed under the Apache License, Version 2.0: http://www.apache.org/licenses/LICENSE-2.0