One clear boundary is the use of Google APIs within Chrome [1]. Chromium derivatives must create and use their own equivalents for things such as Translation, Google Chrome Sync, Updates, etc. which are private Google services and not part of the open source Chromium project.
For extensions, one Google-specific part within Chromium is the chrome.identity API [2] - without it you cannot sign-in to some extensions (e.g. Google Drive). Google has recently released an open-source version of this into Chromium [3] so the boundary you're asking about is becoming a bit more open and clear.
For extensions, one Google-specific part within Chromium is the chrome.identity API [2] - without it you cannot sign-in to some extensions (e.g. Google Drive). Google has recently released an open-source version of this into Chromium [3] so the boundary you're asking about is becoming a bit more open and clear.
[1] https://www.chromium.org/developers/how-tos/api-keys [2] https://developer.chrome.com/docs/extensions/reference/ident... [3] https://chromium-review.googlesource.com/c/chromium/src/+/27...