See how much of a whole page's download actually showed up on screen

A recent release let you point at one thing a page downloaded and see exactly what it painted, or that it painted nothing. This extends that to the whole page at once: it goes through every image, stylesheet, font and hidden beacon a saved page downloaded and scores each one by what it cost you to download versus what it actually put on the screen, then sums it up - 'this much of what this page downloaded showed up as something you can see, and this much was pure weight'. The heaviest downloads are listed first, and the whole report can be sealed into a single result anyone can re-check offline. It is a straight, honest answer to a question every slow, heavy page raises: what was all that downloading actually for?