[Nouveau] Chromium - Application-level nouveau blacklist

[Ilia Mirkin]

It looks like as of Chromium 71, nouveau is completely blacklisted.

I don't really see a way back from this, since they don't cite any
easily reproducible issues, except that some people had some issues
with indeterminate hardware and indeterminate versions of mesa.

In the bug that triggered this
(https://bugs.chromium.org/p/chromium/issues/detail?id=876523), where
I might have slightly lost my cool, they (at the end) suggested that
we try to make nouveau a first-class citizen with chromium. However I
will never be able to present concrete evidence that inconcrete issues
are resolved. I did run the WebGL CTS suite, but that resulted in some
hangs from the the max-texture-size-equivalent test, and some
browser-level weirdness after some tests where later tests all fail
(due to what I have to assume is a browser bug). I don't think I
managed to properly track down the true reason why. I didn't want to
reach out to them with such results, as that's just further evidence
of nouveau not working perfectly.

In the meanwhile, end users are losing accelerated WebGL which in
practice worked just fine (at least in my usage of it), and probably
some other functionality.

One idea is to flip GL_VENDOR to some random string if chromium is
running. I don't like this idea, but I also don't have any great
alternatives. We can also just take this, as yet-another nail in the
nouveau coffin.

Opinions welcome.

Cheers,

  -ilia