It is open source. The icon after a quick search: https://cs.chromium.org/chromium/src/third_party/skia/resour.... Unsure if it's the one that's, say, put in the Windows app manifest. Also unsure if the repo contains all the Chrome resources, but I was under the impression that it did.
https://chromium.googlesource.com/chromium/src/+/lkgr/docs/c... documents the differences on Linux (given it's the only platform which regularly has both packaged). That does seem to miss the EME CDM, though (I'd write a patch for it, but I'm a bit busy at the moment!).
Google Chrome isn't. Chromium is, but Chromium also tends to download 3rd party close-source blobs from online resources, like the one that turns on your microphone.
Based on the link you provided it looks like it's Opt-Out not Opt-In, so it's not really a bug so much as a "feature" that open source software shouldn't have but google wanted to sneak in. based on this link [0] it's pretty clear that they did this intentionally and only changed things after user outcry. I wouldn't call that a bug.
Sounds like the opt-out tracking Mozilla put in, or the advertisement for that TV show it spammed which did stupid things to text. It would be nice to have a mainstream browser which didn't try to track, advertise to, or shove "telemetry" into users.
It wasn't an ad. It shut down before init if you hadn't manually set an about:config value telling it to run.
It was set up in a dumb way, but people also grossly misreported. The extension was "enabled" by default but did exactly nothing except shut itself down. The behavior was all disabled by default.
I'd be surprised if you found the red/yellow/green logo image in chromium