But there are builds of Chromium that support Firefox Sync – Samsung’s Android browser even uses Firefox Sync by default
If you have passwords Xmarks isn't a webextension but you can use it on Firefox 56 and then upgrade.
https://forums.lastpass.com/viewtopic.php?f=45&t=266745&star...
This was a big relief for me, as it was the one extension I was really sweating on.
That said, I would love if there was a Chrome sync for Firefox, or Firefox sync for Chrome capability to sync bookmarks across them both.
Edit: Oh, the wiki page explains that it predates Oracle. So probably the latter.
For the ones that do, like nVidia or Google. The technologies are orders of magnitude more complex now than when they took over their competitors.