Look for devtools global hook

It doesn't exist yet, but it could. And yes, this is basically identical to #953.

This also ensures we actually do our polyfill checks in *all* browsers,
not just Chrome.
navigator.vendor in Firefox === ""
Chrome === "Google Inc."
Safari === "Apple Computer Inc."

Google Inc. may (and does/did) make multiple browsers so Android Browser may show up here. There is unfortunately not any navigator.* property for actual product name so we have to do UA parsing for now.