In whatwg/html#5510 I'm trying to specify <img loading=lazy> in terms of IntersectionObserver as per discussion in whatwg/html#5236

As @domfarolino pointed out, in web specs we try not to call public APIs, but instead want to call the underlying algorithm directly. (Also see #401 )

For lazy-loaded images currently, we need to

• initialize a new IntersectionObserver with a callback that is a set of steps defined in spec prose
• call observe()
• call unobserve()