Chromium is open source, not Chrome.  This may seem like semantics, but when users search the dominant search engine for "chrome web browser" they are going to get directed to Google's version of the browser.  No amount of open source linkfests are going to budge that link from the top of the search results.  As a consequence Chrome will always be exactly what Google wants (or allows) it to be and nothing more.  If Google decides at some future point that ad blockers are eating into its bottom line then the ad blockers will disappear, end of story.  I am sure it will be couched in some pseudo-technical justification (c.f. why adblock won't work on Chrome) but the end result will be the same.  What separates Google from Apple is that at least the latter will have the balls to tell you to your face instead of pretending they don't know what you are talking about.