What key part is closed-source on Windows/Linux?

Maybe "key part" is overstating it a bit, but the auto-update, crash reporting and usage tracking systems are all closed-source, as are the Flash plugin and some non-free audio/video codecs that are bundled with Chrome.

https://code.google.com/p/chromium/wiki/ChromiumBrowserVsGoo...

I think the auto-update, crash reporting and usage tracking code as well as the codecs are open source, they're just not compiled in by default in chromium builds.

Everything. It's only distributed as a binary.

What does this reply even mean? Of course it's distributed as a binary -- should regular users compile it themselves?

Advanced users can compile chromium if they want; from what I understand it's virtually identical to the chrome binary.

If the source code is not available and it's distributed as a binary, by definition it can't be open source. (Plus some might argue about OSS licensing too)

Chromium may be OSS, but Chrome is not.

Yes. Chrome is not Chromium, nor it Opera.

That's what I'm asking: For which part of Chrome is the source code not available?