Info cards float over the page now, instead of hiding it

Every popover in the browser - the page-security card, the Explain this page report, the address-bar suggestions, the command palette, a right-click menu, and the live card you get by hovering a tab - used to hide the whole page while it was open, because the system page view always paints on top of the browser's own interface. Now the interface is lifted in FRONT of the page instead, so a card floats over a page that stays fully visible and LIVE underneath: a video keeps playing, an animation keeps moving, and you can read the card and the page at the same time. Opening and closing a card is flicker-free, with none of the one-frame flashes the first version of this had.