In my main browser profile, I have persistent storage disallowed by default, granting it only for sites that I trust to use it appropriately and feel they would enrich the user experience with how they use it.
For everything else, I use a separate ephemerally-configured browser. It’d be nice if I could at least see build status information on travis-ci.com in my primary browser.
The empherally configured browser is for digitally unhygienic websites operated by companies with questionable motives or poor technology practices. I believe Travis CI isn’t deserving of that designation. You can, and usually do, much better 
Instead, all the privacy-conscious user gets to see right now is a blank page:
Steps:
- Google Chrome (latest stable version, macOS).
- Settings > Content Settings > Cookies: Untick "Allow sites… " (default).
- Open any link to travis-ci.com, for example https://travis-ci.org/wikimedia/mediawiki/ or https://travis-ci.org/wikimedia/mediawiki/jobs/514795757.
I’m pretty sure this is unintentional. It’s a common mistake due to the JavaScript missing the required try/catch clause around one of the statements that reads an optional value from window.localStorage on travis-ci.com. The code already deals with the value being absent, it just needs to also catch the allocation error and treat it the same as if there were no value stored.