More importantly than replay, I'd say is snapshotting. At a high level, if extension writers et al are given an API to snapshot a page at this level there are m

More importantly than replay, I'd say is snapshotting. At a high level, if extension writers et al are given an API to snapshot a page at this level there are many neat things that can be done. One of the biggest is pausing. While some websites will detect long pauses as out of sync most might not see it as any different than a network hiccup, but in general I would like to "pause" any tab not in active focus (maybe except a whitelist like my email). All of the suspension tools in browsers that I'm aware of just store the URL and kill the page, just to reload from that URL in "restore". I can think of about a dozen other use cases for browser-tab serialization (i.e. snapshotting), esp wrt distribution, remote use, caching, render-and-stop read-only pages, etc.