Attempts to turn the preference on for WPT tests have failed so far due to too many new timeouts and intermittent failures related to the RemoteContextHelper test feature. This issue tracks the known outstanding work to turn the feature on:

• Navigation incorrectly defaults to history pushing in most cases #39818 (script: Do not force push history handling. #39896)
• New timers scheduled after traversing history don't fire #39545 (script: Ensure scheduled timers account for suspension offset. #39880)
• Going forward in history does not trigger pageshow #39798 (constellation: Unload documents when traversing session history. #39871)
• Websockets do not prevent bfcache #39872 (script: Mark document as unsalvageable if unclosed websockets present. #39940)
• Discarded documents can be reloaded with outdated URLs #39903 (constellation: Update the stored URL when discarding a document. #39941)