Comment by SllX
So a couple of things.
1) Apple would never force "Chromium" on any of their platforms. You might be mistaking it for WebKit, but browsers are not required to use Apple's shipping version of WebKit on a Mac either.
2) Firefox on every single platform not on the iPhone & iPad uses and has always used Gecko. I'm not aware of any other exceptions besides those two platforms, but the Mac definitely isn't one of them.