Pages that measure themselves while loading render faster

A profile of a real page load turned up something worth fixing. When a page asks where its own elements are while it is still loading - which React and design-system layouts do constantly during startup, to size a sidebar or a carousel - the engine answers by laying the page out on the spot. Each of those answers was re-reading and re-parsing the page's entire stylesheet from scratch, even though the stylesheet never changes between one measurement and the next; only the page content does. On a large site that stylesheet is several megabytes and the page measures itself a dozen times over, so the same parse was being redone again and again for nothing. Now the parsed stylesheet and its lookup index are remembered and reused as long as the styles are unchanged, including for pages built from web components with their own shadow styles. The result is a measurable cut - around eight percent - to the script-driven layout work on the sites tested, with byte-for-byte identical output: the rendering is exactly the same, just reached with less repeated work. The engine gate holds at 6375 of 6375.