Google is cutting down on the extensions ability to read and modify your web requests on the fly. As a side effect adblocker type extensions need to pass their blacklist patterns to chrome which will enforce it on their behalf. Chrome cites improved privacy because users won't need to give random extensions full read write access to pretty much all their online activities and performance gains because arbitrary adblocking code cannot run anymore and it needs to be in form of a blacklist patterns. Lastly Apple Safari has been doing the same all along.
The opponent arguments (expressed in the article and by many people leaving comments here) are that this kneecaps some AdBlock extensions because they need to run arbitrary code as the declarative API is not flexible enough for them and this is part of Google covert plan to kill adblocking.
I personally agree with the Chrome team's argument here