How did Google Chrome just update itself when I had forcefully disabled updates and removed Google Update?

Here's the deal -- I just didn't want my Chrome installation to update, for certain reasons that are irrelevant here:

• I'd disabled Google Update in the Group Policy (yes, I know Chrome ignores it)
• I'd disabled the Google Update services
• I'd uninstalled Google Update (not that Google was honest enough to make this work, but still)
• I'd even removed the Google Update program files in C:\Program Files manually

...and this was working for many weeks... until yesterday!

Until yesterday, Chrome kept nagging me with its usual Chrome-is-out-of-date and Chrome-is-broken-please-reinstall popups. And if I tried to manually update Chrome, it failed -- it gave error 0x80040154. So I knew I was doing something right (or wrong, depending on your point of view).

But today morning I woke up only to find that Chrome had magically updated itself, which drove me very angry and confused at Google. So in one sentence, here's my question:

How did Google force-push an update to my Chrome despite my actions?

Some follow-up questions that are on my mind right now:

Is this in the Chromium source code somewhere, or is it a Google Chrome-specific feature?
Is this a well-known capability? Has it ever been publicized before? Has Google acknowledged it?
From my perspective it seems quite dishonest to "backdoor" this so slyly, and I didn't know they would.
Heck, is someone at Google monitoring my installation or something?