Web updates

HTML b3b7add4cfb9

Change beforeunload, unload, and bfcache interaction Per, removes the requirement that beforeunload event listeners being fired cause a document to become unsalveagable (i.e., ineligible for bfcache). Instead, unsalveagability is left more explicitly up to the user agent. Additionally, changes navigation to no longer dispatch unload events for documents which are kept alive in the session history (bfcache). Closes #5748.

Rakina Zata Amni