Google has announced that it is cutting off access to the Sync and "other Google Exclusive" APIs from all builds except Google Chrome. This will make the Fedora Chromium build significantly less functional (along with every other distro packaged Chromium). It is noteworthy that Google gave the builders of distribution Chromium packages these access rights back in 2013 via API keys, specifically so that we could have open source builds of Chromium with (near) feature parity to Chrome. And now they're taking it away. The reasoning given for this change? Google does not want users to be able to "access their personal Chrome Sync data (such as bookmarks) ... with a non-Google, Chromium-based browser." They're not closing a security hole, they're just requiring that everyone use Chrome.
Or to put it bluntly, they do not want you to access their Google API functionality without using proprietary software (Google Chrome). There is no good reason for Google to do this, other than to force people to use Chrome.
I would say that you might want to reconsider whether you want to use Chromium or not. If you want the full "Google" experience, you can run the proprietary Chrome. If you want to use a FOSS browser that isn't hobbled, there is a Firefox package in Fedora.