Chrome OS app localStorage polyfill
Surprinsingly Chrome OS apps don't have access to window.localStorage.
In this repo I provide a simple app with an example implementation for localStorage. You cannot simply use window.localStorage = chrome.storage.local because chrome.storage is async. Check the docs.
This polyfill works as a drop in replacement with a single gotcha: you need to wait for a promise before you can read from window.localStorage. The code is straightforward so you could replace that promise with an event, a signal, or whatever works best for your project.
I'm using ES6 without Babel because at this point Chromebooks can be considered evergreen browsers.