Check for IntersectionObserverEntry.prototype.isIntersecting

[dieulot]

quicklink is using isIntersecting but not all browsers that implement IntersectionObserver implement isIntersecting. The culprits are Edge 15 and Chrome 51–57. UC Browser is based on Chromium 57 so this is useful even for a “modern” browser.

Note that I didn’t test this (but it’s the pattern I use for instant.page).