Web updates

HTML 9bed042ab3f4

Move Page Visibility APIs into HTML Defines the document.hidden and document.visibilityState APIs in the HTML Standard, while improving their definitions to be more rigorous. This is similar to 3285b988b8e962d9692e547fd3101ceb23cb1cb6 which did the same for the visibilitychange event. Also updates the discussion of "page is in the background" to refer to the new definitions. See and for more background.

Noam Rosenthal