Mozilla's relationship with Google also isn't set in stone. Yahoo was the main sponsor for a while.
For better or for worse, I would still say it's the anti-chrome. Find me another crossplatform browser with a stack that's still as independent as Mozilla's. They have the engine, the add-on store, and everything in between.
I would be using Opera right now but they threw in the towel years ago. Now the brand is being milked by a private equity firm.
Mozilla literally makes Google the default search engine.
If new scary stuff starts showing up in Firefox of source code where the auto sign you into google, or strangely start turning away from web standards and towards Google supported proprietary initiatives, or something like that, that would put some meat into the nothing burger.