Earlier quoted context omitted.
> Google doesn't have control of Chromium though. They do. If they merge DRM into it tomorrow or something alike, it trickles down to all users of Chromium and Google Chrome. You can build _a fork_ of it. But the enormous majority of the masses don’t use your fork — they use upstream.
Chromium is upstream of Chrome, not the other way around. However, Google Chrome is so ubiquitous that any changes Google makes to it are expected to be available in all other browsers and its a kind of defacto control even if it isn't technically control of the upstream Chromium project.
They do have technical control over the upstrean Chromium project. There's an invite only pool of developers who decide what gets committed to Chromium and they are Google employees.