WebExtensions: modify about:home

I’ve been working on a start page extender for a while now, but I just found out all the older technologies are being phased out soon, so I guess I have to migrate. In the past I accomplished this by

  1. from bootstrap.js, assembling and saving a custom start page based on about:home, then
  2. using Components.manager.addBootstrappedManifestLocation to load a chrome.manifest which
  3. contained three override chrome://browser/content/abouthome/aboutHome.xhtml modified.xhtml statements to implement my modified js, css, and xhtml files for the rest of the session

This was fast, and it worked well. I’ve spent hours already and I just can’t figure out how to accomplish the same thing with WebExtensions. Can someone please point me in the right direction?

Thanks for reading.

There are new APIs that you can use:

“chrome_settings_overrides” is only available from FF55