There's still a lot of static theme and built-in theme stuff that depends on the LightweightThemeManager infrastructure that needs some care to get rid of. But there's also a lot of extraneous crap that touches LightweightThemeManager where it should just use AddonManager, and the LWT web install stuff, which we can get rid of much more easily, and sooner.

Does this get rid of theme switching from customize entirely? It would be pretty weird to have recommendations (A Web Browser Renaissance, et al), but not have installed themes shown there (especially because there is a header labeled "My Themes" containing the built in themes... which aren't exactly "mine").

I will say, I really like the preview as well in that dropdown as well - it feels super discoverable.

(In reply to Asif Youssuff from comment #10)

Does this get rid of theme switching from customize entirely?

No, although that's planned in bug 1515211.

https://hg.mozilla.org/mozilla-central/rev/e711fcd0a02d
https://hg.mozilla.org/mozilla-central/rev/5cb9e990d8e3
https://hg.mozilla.org/mozilla-central/rev/85e270253e04
https://hg.mozilla.org/mozilla-central/rev/7262fc6d3c83
https://hg.mozilla.org/mozilla-central/rev/28358411c6b3
https://hg.mozilla.org/mozilla-central/rev/1b6a74704287
https://hg.mozilla.org/mozilla-central/rev/0467cc193a74
https://hg.mozilla.org/mozilla-central/rev/d9c0bc33eea6
https://hg.mozilla.org/mozilla-central/rev/ce04183ab703